Skip to main content
NCBI home page
British Journal of Pharmacology logoLink to British Journal of Pharmacology
. 2006 May 8;148(4):452–458. doi: 10.1038/sj.bjp.0706762

AT2 receptor-mediated vasodilation in the mouse heart depends on AT1A receptor activation

Joep H M van Esch 1, Martin P Schuijt 1, Jilani Sayed 1, Yawar Choudhry 1, Thomas Walther 1, A H Jan Danser 1,*
PMCID: PMC1751777  PMID: 16682962

Abstract

  1. Angiotensin (Ang) II type 2 (AT2) receptors are believed to counteract Ang II type 1 (AT1) receptor-mediated effects. Here, we investigated AT2 receptor-mediated effects on coronary and cardiac contractility in C57BL/6 mice.

  2. Hearts were perfused according to Langendorff. Baseline coronary flow (CF) and left ventricular systolic pressure (LVSP) were 2.7±0.1 ml min−1 and 111±3 mmHg (n=50), respectively.

  3. Ang II (n=14) concentration dependently decreased CF and LVSP, by maximally 41±4 and 25±3%, respectively (pEC50s 7.41±0.12 and 7.65±0.12). The AT1 receptor antagonist irbesartan (n=4) abolished all Ang II-induced changes, whereas the AT2 receptor antagonist PD123319 (n=6) enhanced (P<0.05) the effect of Ang II on CF (to 59±1%) and LVSP (to 44±2%), without altering its potency. A similar enhancement was observed in the presence of nitric oxide (NO) synthase inhibitor Nω-nitro-L-arginine methyl ester HCl (L-NAME; n=4). On top of L-NAME, PD123319 no longer affected the response to Ang II (n=4).

  4. The AT2 receptor agonist CGP42112A (n=4) did not affect CF or LVSP, nor did CGP42112A (n=4) alter the constrictor response to the α1-adrenoceptor agonist phenylephrine. Furthermore, Ang II exerted no effects in hearts of AT1A−/− mice (n=5), whereas its effects in hearts of AT1A+/+ wild-type control mice (n=7) were indistinguishable from those in hearts of C57BL/6 mice.

  5. In conclusion, Ang II exerts opposite effects on coronary and cardiac contractility in the mouse heart via activation of AT1A and AT2 receptors. AT2 receptor-mediated effects depend on NO and occur only in conjunction with AT1A receptor activation.

Keywords: Angiotensin II, vasodilation, coronary artery, mouse, Langendorff model

Introduction

The renin–angiotensin system (RAS) plays an important role in the regulation of blood pressure, cardiovascular remodeling and maintaining body fluid volume. The main effector peptide of the RAS, angiotensin (Ang) II, activates Ang II type 1 (AT1) and Ang II type 2 (AT2) receptors. Two subtypes of AT1 receptor have been identified in rodents (AT1A and AT1B) which share 94% sequence homology, whereas the AT2 receptor only shares 34% sequence homology with these subtypes (Elton et al., 1992; Iwai & Inagami, 1992; Mukoyama et al., 1993). AT1 receptors mediate the well-known vasoconstrictor, inotropic, chronotropic, aldosterone-releasing, noradrenaline-releasing and growth-stimulatory effects of Ang II, and AT2 receptors are generally assumed to counteract these actions (Hein et al., 1995; Ichiki et al., 1995; Munzenmaier & Greene, 1996; van Kesteren et al., 1997; Masaki et al., 1998; Siragy et al., 1999; Schuijt et al., 2001; Batenburg et al., 2004). It is believed that AT2 receptor-mediated vasodilation is an endothelium-dependent phenomenon, involving bradykinin type 2 receptors, nitric oxide (NO) and guanosine cyclic 3′, 5′-monophosphate (Siragy & Carey, 1997; Tsutsumi et al., 1999; Katada & Majima, 2002; Hannan et al., 2003; Batenburg et al., 2005).

However, not all studies confirm the counter-regulatory actions of AT2 receptors (Levy et al., 1996; Ichihara et al., 2001; Duke et al., 2005; You et al., 2005). Findings on AT2 receptor-mediated effects that contrasted with the above concept have been attributed to disparities in genetic background (Schneider & Lorell, 2001) or blood pressure (You et al., 2005). Furthermore, in many studies, conclusions on AT2 receptor-mediated counteracting effects were drawn based on indirect evidence, that is, the occurrence of an enhanced response to Ang II following AT2 receptor antagonism or gene disruption (Hein et al., 1995; Ichiki et al., 1995; Schuijt et al., 2001; Hannan et al., 2003). The interpretation of data obtained in the absence of AT2 receptors is complex, because AT2 receptors downregulate AT1 receptors in a ligand-independent manner (Jin et al., 2002), and AT2 receptor-null mice display increased AT1 receptor expression (Tanaka et al., 1999).

In the present study, we set out to characterize AT2 receptor-mediated effects in the coronary vascular bed of the mouse heart using the Langendorff model. Despite the many AT2 receptor-related studies in transgenic mice, such data are currently not available. AT2 receptor-mediated responses were studied by comparing Ang II-induced responses in the absence and presence of the AT2 receptor antagonist PD123319, and by selectively stimulating AT2 receptors. The latter was accomplished in three ways. First, we investigated the effects of Ang II in the presence of the AT1 receptor antagonist irbesartan. Second, we studied the effects of the AT2 receptor agonist CGP42112A (Yee et al., 1998; Barber et al., 1999; Li & Widdop, 2004), both at baseline and during phenylephrine-induced vasoconstriction. Third, we evaluated the response to Ang II in AT1A−/− mice, that is, mice lacking Ang II-induced vasoconstriction (Ito et al., 1995). We also investigated whether NO mediated the AT2 receptor-dependent responses using the NO synthase (NOS) inhibitor Nω-nitro-L-arginine methyl ester HCl (L-NAME).

Methods

Animals

Male C57BL/6 mice (26±0.6 g; n=50) were obtained from Harlan (Zeist, The Netherlands). Male AT1A+/+ (31±1 g; n=7) and AT1A−/− mice (27±2 g; n=5) were bred on a 129 × C57BL/6 background at the animal facilities of the Charité, Campus Benjamin Franklin, Berlin, Germany (Oliverio et al., 1997). All experiments were performed under the regulation and permission of the Animal Care Committee of the Erasmus MC, Rotterdam, The Netherlands.

Drugs

Ang II, CGP42112A, PD123319, bradykinin, endothelin-1, phenylephrine and L-NAME were purchased from Sigma (Zwijndrecht, The Netherlands). Irbesartan was a kind gift of Sanofi-Synthelabo BV (Gouda, The Netherlands). Irbesartan (10 mM) was dissolved in ethanol whereas all other chemicals were dissolved in water. Stock solutions were stored in aliquots at −80°C and diluted in modified Krebs–Henseleit (KH) perfusion buffer (composition in mM: NaCl 118, KCl 4.7, MgSO4 1.2, KH2PO4 1.2, CaCl2 1.2, D-glucose 11, NaHCO3 25 and pyruvic acid 2) on the day of the experiment. All perfusion solutions were passed through a 0.46 μm cellulose acetate filter (Millipore, Billerica, MA, U.S.A.) before their application in the Langendorff setup.

Langendorff preparation

Mice were heparinized using heparin (200 IU; i.p.) and subsequently killed by cervical dislocation (Gustafson & van Beek, 2000). The heart was rapidly excised and placed in ice-cold modified KH buffer, gassed with 95% O2 and 5% CO2 (Gustafson & van Beek, 2000; Wang et al., 2002). The aorta was immediately cannulated with a 19G needle (with a small circumferential grove close to the blunt tip) and perfused with gassed KH buffer according to Langendorff at a constant perfusion pressure of 80 mmHg (Sutherland et al., 2003). Two needle electrodes were placed at the right atrium and the hearts were paced at ∼600 b.p.m. (5 Hz, 4 min duration, 4 V) using a Grass stimulator (Grass Instruments Co., Quincy, MA, U.S.A.).

Left ventricular systolic pressure (LVSP) was measured with a water-filled balloon (made of domestic food wrap) connected to a disposable pressure transducer (Braun, Melsungen, Germany). The left atrium was removed and the balloon was inserted into the left ventricle (Curtis et al., 1986; Sutherland et al., 2003). The left ventricular end-diastolic pressure was set at 3–5 mmHg by adjusting the balloon volume. Coronary flow (CF) was measured with a flow probe (Transonic systems, Ithaca, NY, U.S.A.).

Experimental protocol

After a stabilization period of 10–15 min, baseline values of CF and LVSP were obtained. Next, bolus injections (100 μl) of modified KH buffer were applied three times to determine injection-induced changes in CF and LVSP. Subsequently, bolus injections (100 μl) of Ang II, CGP42112A, bradykinin or endothelin-1 (concentration range in the injection fluid 0.1 nM–0.1 mM) were applied, in the absence or presence of irbesartan (1 μM in the perfusion buffer), PD123319 (1 μM) and/or the NOS inhibitor L-NAME (10 mM). All blockers were present in the perfusion buffer starting 15 min before the first bolus injection. CGP42112A-induced effects were also studied in combination with the α1-adrenoceptor agonist phenylephrine, by injecting 1 mM phenylephrine alone or simultaneously with 0.1 μM CGP42112A.

Data analysis

CF and LVSP data were recorded and digitalized using WinDaq waveform recording software (Dataq Instruments, Akron, OH, U.S.A.). After a manual selection of the desired signals pre- and post-injection, data were analyzed using Matlab (Mathworks Inc., Natick, MA, U.S.A.). Six consecutive beats were selected for determination of CF and LVSP.

Data are given as mean±s.e.m. and represent percentage change from baseline. Concentration–response curves were analyzed as described (DeLean et al., 1978), using Graph Pad Prism 3.01 (Graph Pad Software Inc., San Diego, CA, U.S.A.), to obtain pEC50 (−10logEC50) and Emax values. The pEC50 values refer to the agonist concentration in the injection fluid and do not reflect the actual concentrations seen by the receptor. Statistical analysis between groups was by Student's t-test or one-way analysis of variance, followed by post hoc evaluation according to Dunnet. P<0.05 was considered significant.

Results

Baseline hemodynamic values and effect of KH buffer injection

Baseline CF values were 2.7±0.1 ml min−1 (n=50), 2.7±0.2 ml min−1 (n=5) and 2.5±0.2 ml min−1 (n=8) in C57BL/6 mice, AT1A−/− mice and AT1A+/+ wild-type control mice, respectively. Baseline LVSP values were 111±3, 114±8 and 99±4 mmHg, respectively. KH buffer injections did not significantly affect these baseline parameters (Figures 1, 2, 3 and 4).

Figure 1.

Figure 1

Open in a new tab

Left panels, effects of Ang II bolus injections (100 μl) on CF and LVSP in the mouse Langendorff heart in the absence (control; n=14) or presence of 1 μM irbesartan (n=4) or 1 μM PD123319 (n=6). Right panels, effects of Ang II bolus injections on CF and LVSP in the mouse Langendorff heart in the presence of 1 μM L-NAME with or without 1 μM PD123319 (n=4 for both conditions). The x-axis displays the Ang II concentration in the injection fluid. Data are mean±s.e.m. and represent percentage change from baseline. KH, bolus injection of Krebs–Henseleit buffer. *P<0.05 vs control.

Figure 2.

Figure 2

Open in a new tab

Left panels, effects of CGP42112A (n=4) bolus injections (100 μl) on CF and LVSP in C57BL/6 mice. The x-axis displays the concentration in the injection fluid. KH, bolus injection of Krebs–Henseleit buffer. Right panels, effects of a phenylephrine bolus injection (100 μl of a solution containing 1 mM phenylephrine), with or without 0.1 μM CGP42112A (n=4 for both conditions), on CF and LVSP in the mouse Langendorff heart. Data are mean±s.e.m. and represent percentage change from baseline.

Figure 3.

Figure 3

Open in a new tab

Effect of bradykinin bolus injections (100 μl) on CF and LVSP in the mouse Langendorff heart. Data are mean±s.e.m. of six experiments and represent percentage change from baseline. KH, bolus injection of Krebs–Henseleit buffer.

Figure 4.

Figure 4

Open in a new tab

Effects of Ang II bolus injections on CF and LVSP in AT1A−/− (n=5) and the corresponding AT1A+/+ (wild-type control; n=7) mice. The x-axis displays the concentration in the injection fluid. Data are mean±s.e.m. and represent percentage change from baseline. KH, bolus injection of Krebs–Henseleit buffer. *P<0.05 vs AT1A+/+.

Studies in C57BL/6 mice

Ang II (n=14) concentration dependently decreased CF and LVSP, by maximally 41±4 and 25±3%, respectively (pEC50s 7.41±0.12 and 7.65±0.12; Figure 1). Ang II concentrations >1 μM did not result in effects that were larger than those observed at 1 μM, in agreement with the concept of receptor desensitization (Abdellatif et al., 1991; Reagan et al., 1993; Iglesias et al., 2001). The Ang II effects were maximal within 10–20 and 20–30 s for CF and LVSP, respectively. Values returned to baseline after 0.5–1 min.

Irbesartan (n=4) abolished all Ang II-induced changes. In contrast, PD123319 (n=6) enhanced the effect of Ang II on CF (to 59±1%; P<0.05 vs control) and LVSP (to 44±2%; P<0.05 vs control), without altering its potency (pEC50s 7.41±0.12 and 7.49±0.20, respectively). L-NAME (n=4) similarly enhanced (P<0.05) the effect of Ang II on CF (to 57±1%) and LVSP (to 35±2%), without altering its potency (pEC50s 6.95±0.34 and 7.22±0.13, respectively; Figure 1). PD123319 (n=4) no longer enhanced the effect of Ang II on top of L-NAME, thereby indicating that its effect depends on NO.

Phenylephrine (n=4) decreased CF and LVSP (Figure 2, P<0.05). CGP42112A (n=4) did not diminish the constrictor and inotropic response to phenylephrine, nor did this AT2 receptor agonist (n=4) exert constrictor or inotropic effects of its own (Figure 2). Bradykinin (n=6) increased CF by maximally 42±6% and marginally affected LVSP (Figure 3).

Studies in AT1A−/− mice

Ang II (n=5) did not affect CF or LVSP in AT1A−/− mice, whereas the Ang II (n=7) response in AT1A+/+ wild-type control mice was indistinguishable from that in C57BL/6 mice (Figures 1, 4 and 5). Endothelin-1 (0.1 nM) decreased CF in both AT1A−/− and AT1A+/+ wild-type control mice (Figure 5). The endothelin-1-induced decreases in CF and LVSP (47±15 and 41±10%, respectively) were comparable to those induced by 1 mM phenylephrine (Figure 4).

Figure 5.

Figure 5

Open in a new tab

Representative tracings showing the effects of a bolus injection (100 μl; arrow) containing 1 μM Ang II or 0.1 nM endothelin-1 (ET-1) on CF in AT1A+/+ (wild-type control; left panels) and AT1A−/− (right panels) mice.

Discussion

This study is the first to support the concept of AT2 receptor-mediated vasodilation in the mouse coronary vascular bed. Evidence for such vasodilation was obtained indirectly, that is, as an enhanced constrictor response to Ang II in the presence of the AT2 receptor antagonist PD123319. Data are in full agreement with previous studies on this matter in human (Batenburg et al., 2004), porcine (Zhang et al., 2003), rabbit (Pörsti et al., 1993) and rat (Schuijt et al., 2001) coronary arteries.

Vasodilation did not occur when exposing the mouse heart to Ang II in the presence of irbesartan (a condition allowing selective AT2 receptor stimulation, which has been used successfully in previous studies; Munzenmaier & Greene, 1996; Widdop et al., 2002; Batenburg et al., 2004), nor during exposure of the heart to the AT2 receptor agonist CGP42112A. This was not due to an inability to detect vasodilation, as bradykinin exerted its well-known vasodilator effects in our Langendorff setup. Furthermore, Ang II exerted no effect in hearts of AT1A−/− mice, although these mice do express AT2 receptors (Harada et al., 1998; Ryan et al., 2004). This demonstrates first that the AT1A receptor is the receptor responsible for coronary vasoconstriction, in agreement with the observation that deletion of the AT1A receptor (Ito et al., 1995), but not of the AT1B receptor (Chen et al., 1997), virtually abolishes the in vivo vasoconstrictor response to Ang II and reduces blood pressure. Secondly, it demonstrates that stimulation of AT2 receptors in the absence of AT1A receptors also does not result in vasodilation.

It has been suggested that AT2 receptor-mediated vasodilation can only be observed in hypertensive (and not normotensive) animals (Li & Widdop, 2004). Thus, concomitant vasoconstriction might be a prerequisite to observe AT2 receptor-mediated vasodilation. However, in contrast with this concept, CGP42112A did not affect the vasoconstrictor response to the α1-adrenoceptor agonist phenylephrine in the mouse heart.

It appears therefore that AT2 receptor-mediated effects depend on simultaneous AT1A receptor activation, for instance because both receptors heterodimerize (AbdAlla et al., 2001), or because interaction occurs at the postreceptor level. Heterodimerization would require the simultaneous occurrence of both receptors in the same (smooth muscle) cell, and although this concept has been tested in smooth muscle cells of transgenic mice (Nakajima et al., 1995; Tsutsumi et al., 1999), most studies suggest that AT2 receptors are restricted to endothelial cells (Stoll et al., 1995; Muller et al., 1998; Batenburg et al., 2004), whereas AT1 receptors are mainly located on smooth muscle cells.

AT2 receptor-mediated responses, in contrast with AT1 receptor-mediated constriction, depend on both endothelial and smooth muscle cells, and involve a cascade starting with endothelial bradykinin type 2 receptor activation and subsequent NO synthesis, and finally resulting in guanylyl cyclase activation in smooth muscle cells (Tsutsumi et al., 1999; Hannan et al., 2003; Batenburg et al., 2005). In agreement with the important contribution of NO to the vasodilator effect of the AT2 receptor, L-NAME enhanced the Ang II response to the same degree as PD123319, and PD123319 no longer enhanced the effect of Ang II in the presence of L-NAME.

The question then arises why direct, AT2 receptor-mediated vasodilation could not be observed in the present study. First, although several groups have demonstrated such vasodilation in various species (including humans), both in vitro and in vivo (Endo et al., 1998; Dimitropoulou et al., 2001; Katada & Majima, 2002; Widdop et al., 2002; Batenburg et al., 2004), we are not aware of studies in mice showing Ang II-induced vasodilation. Thus, the simplest explanation is that mice differ from other species, in that their coronary AT2 receptors are not limited to endothelial cells. Indeed, Utsunomiya et al. (2005) observed abundant AT2 receptor protein immunoreactivity in the media of mouse coronary arteries. Second, Widdop et al. (2003) have suggested that the sensitivity of some experimental preparations is too low to observe AT2 receptor-induced vasodilation. However, based on the robust (≈50%) PD123319-induced increase of the coronary constrictor response to Ang II, a considerable degree of vasodilation should have occurred in our preparation during selective AT2 receptor stimulation, and such robust vasodilation was in fact present when exposing the heart to bradykinin, the putative mediator of the AT2 receptor-mediated relaxation. Finally, application of Ang II via bolus injections differs greatly from the local production of Ang II in close proximity of AT1 and AT2 receptors (van Kats et al., 1998; Schuijt et al., 2002; Tom et al., 2003) that occurs in vivo, and thus, one further possibility is that arterial Ang II delivery is an inappropriate tool to observe AT2 receptor-mediated vasorelaxation.

PD123319 enhanced the negative inotropic response to Ang II in the mouse heart. This suggests that AT2 receptors counteract the AT1 receptor-mediated negative inotropic effects in mouse cardiomyocytes. However, selective AT2 receptor stimulation did not affect cardiac inotropy. Combined with the observation that AT2 receptors do not occur in cardiomyocytes (Utsunomiya et al., 2005), a more likely explanation is that the inotropic effects of Ang II in the mouse heart are a consequence of its effects on CF rather than the consequence of direct stimulation of AT1 and/or AT2 receptor on cardiomyocytes. This may be different under pathological conditions, for example, following myocardial infarction, when AT2 receptors improve left ventricular systolic function (Yang et al., 2002).

In summary, our study provides evidence for opposite effects of AT1A and AT2 receptors in the coronary vascular bed of normotensive mice. AT2 receptor-mediated effects depended on NO and occurred only in conjunction with AT1A receptor activation. The latter observation suggests that AT1A and AT2 receptors display an interaction, either directly (due to receptor heterodimerization) or at the postreceptor level. Such interaction might be of particular importance under conditions where the RAS is stimulated, for example, during sodium depletion or in subjects with renovascular hypertension. A similar functional interaction has been described between the Ang-(1–7) receptor Mas and AT1 and AT2 receptors (Castro et al., 2005). Future investigations should elucidate the exact site of AT1A–AT2 receptor interaction and whether the interaction is altered under pathological conditions.

Acknowledgments

We thank Rob H. van Bremen and Dr Daphne Merkus of the Department of Experimental Cardiology (Erasmus MC, Rotterdam, The Netherlands) for their help with the analysis of the data.

Abbreviations

Ang

angiotensin

AT1 receptor

angiotensin II type 1 receptor

AT2 receptor

angiotensin II type 2 receptor

CF

coronary flow

KH

Krebs–Henseleit

L-NAME

Nω-nitro-L-arginine methyl ester HCl

LVSP

left ventricular systolic pressure

NO

nitric oxide

NOS

nitric oxide synthase

RAS

renin–angiotensin system

References

  1. ABDALLA S., LOTHER H., ABDEL-TAWAB A.M., QUITTERER U. The angiotensin II AT2 receptor is an AT1 receptor antagonist. J. Biol. Chem. 2001;276:39721–39726. doi: 10.1074/jbc.M105253200. [DOI] [PubMed] [Google Scholar]
  2. ABDELLATIF M.M., NEUBAUER C.F., LEDERER W.J., ROGERS T.B. Angiotensin-induced desensitization of the phosphoinositide pathway in cardiac cells occurs at the level of the receptor. Circ. Res. 1991;69:800–809. doi: 10.1161/01.res.69.3.800. [DOI] [PubMed] [Google Scholar]
  3. BARBER M.N., SAMPEY D.B., WIDDOP R.E. AT(2) receptor stimulation enhances antihypertensive effect of AT(1) receptor antagonist in hypertensive rats. Hypertension. 1999;34:1112–1116. doi: 10.1161/01.hyp.34.5.1112. [DOI] [PubMed] [Google Scholar]
  4. BATENBURG W.W., GARRELDS I.M., BERNASCONI C.C., JUILLERAT-JEANNERET L., VAN KATS J.P., SAXENA P.R., DANSER A.H.J. Angiotensin II type 2 receptor-mediated vasodilation in human coronary microarteries. Circulation. 2004;109:2296–2301. doi: 10.1161/01.CIR.0000128696.12245.57. [DOI] [PubMed] [Google Scholar]
  5. BATENBURG W.W., TOM B., SCHUIJT M.P., DANSER A.H.J. Angiotensin II type 2 receptor-mediated vasodilation. Focus on bradykinin, NO and endothelium-derived hyperpolarizing factor(s) Vasc. Pharmacol. 2005;42:109–118. doi: 10.1016/j.vph.2005.01.005. [DOI] [PubMed] [Google Scholar]
  6. CASTRO C.H., SANTOS R.A., FERREIRA A.J., BADER M., ALENINA N., ALMEIDA A.P. Evidence for a functional interaction of the angiotensin-(1–7) receptor Mas with AT1 and AT2 receptors in the mouse heart. Hypertension. 2005;46:937–942. doi: 10.1161/01.HYP.0000175813.04375.8a. [DOI] [PubMed] [Google Scholar]
  7. CHEN X., LI W., YOSHIDA H., TSUCHIDA S., NISHIMURA H., TAKEMOTO F., OKUBO S., FOGO A., MATSUSAKA T., ICHIKAWA I. Targeting deletion of angiotensin type 1B receptor gene in the mouse. Am. J. Physiol. 1997;272:F299–F304. doi: 10.1152/ajprenal.1997.272.3.F299. [DOI] [PubMed] [Google Scholar]
  8. CURTIS M.J., MACLEOD B.A., TABRIZCHI R., WALKER M.J. An improved perfusion apparatus for small animal hearts. J. Pharmacol. Methods. 1986;15:87–94. doi: 10.1016/0160-5402(86)90008-2. [DOI] [PubMed] [Google Scholar]
  9. DELEAN A., MUNSON P.J., RODBARD D. Simultaneous analysis of families of sigmoidal curves: application to bioassay, radioligand assay, and physiological dose–response curves. Am. J. Physiol. 1978;235:E97–E102. doi: 10.1152/ajpendo.1978.235.2.E97. [DOI] [PubMed] [Google Scholar]
  10. DIMITROPOULOU C., WHITE R.E., FUCHS L., ZHANG H., CATRAVAS J.D., CARRIER G.O. Angiotensin II relaxes microvessels via the AT(2) receptor and Ca(2+)-activated K(+) (BK(Ca)) channels. Hypertension. 2001;37:301–307. doi: 10.1161/01.hyp.37.2.301. [DOI] [PubMed] [Google Scholar]
  11. DUKE L.M., EVANS R.G., WIDDOP R.E. AT2 receptors contribute to acute blood pressure-lowering and vasodilator effects of AT1 receptor antagonism in conscious normotensive but not hypertensive rats. Am. J. Physiol. Heart Circ. Physiol. 2005;288:H2289–H2297. doi: 10.1152/ajpheart.01096.2004. [DOI] [PubMed] [Google Scholar]
  12. ELTON T.S., STEPHAN C.C., TAYLOR G.R., KIMBALL M.G., MARTIN M.M., DURAND J.N., OPARIL S. Isolation of two distinct type I angiotensin II receptor genes. Biochem. Biophys. Res. Commun. 1992;184:1067–1073. doi: 10.1016/0006-291x(92)90700-u. [DOI] [PubMed] [Google Scholar]
  13. ENDO Y., ARIMA S., YAOITA H., TSUNODA K., OMATA K., ITO S. Vasodilation mediated by angiotensin II type 2 receptor is impaired in afferent arterioles of young spontaneously hypertensive rats. J. Vasc. Res. 1998;35:421–427. doi: 10.1159/000025613. [DOI] [PubMed] [Google Scholar]
  14. GUSTAFSON L.A., VAN BEEK J.H. Measurement of the activation time of oxidative phosphorylation in isolated mouse hearts. Am. J. Physiol. Heart Circ. Physiol. 2000;279:H3118–H3123. doi: 10.1152/ajpheart.2000.279.6.H3118. [DOI] [PubMed] [Google Scholar]
  15. HANNAN R.E., DAVIS E.A., WIDDOP R.E. Functional role of angiotensin II AT2 receptor in modulation of AT1 receptor-mediated contraction in rat uterine artery: involvement of bradykinin and nitric oxide. Br. J. Pharmacol. 2003;140:987–995. doi: 10.1038/sj.bjp.0705484. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. HARADA K., KOMURO I., SHIOJIMA I., HAYASHI D., KUDOH S., MIZUNO T., KIJIMA K., MATSUBARA H., SUGAYA T., MURAKAMI K., YAZAKI Y. Pressure overload induces cardiac hypertrophy in angiotensin II type 1A receptor knockout mice. Circulation. 1998;97:1952–1959. doi: 10.1161/01.cir.97.19.1952. [DOI] [PubMed] [Google Scholar]
  17. HEIN L., BARSH G.S., PRATT R.E., DZAU V.J., KOBILKA B.K. Behavioural and cardiovascular effects of disrupting the angiotensin II type-2 receptor in mice. Nature. 1995;377:744–747. doi: 10.1038/377744a0. [DOI] [PubMed] [Google Scholar]
  18. ICHIHARA S., SENBONMATSU T., PRICE E., JR, ICHIKI T., GAFFNEY F.A., INAGAMI T. Angiotensin II type 2 receptor is essential for left ventricular hypertrophy and cardiac fibrosis in chronic angiotensin II-induced hypertension. Circulation. 2001;104:346–351. doi: 10.1161/01.cir.104.3.346. [DOI] [PubMed] [Google Scholar]
  19. ICHIKI T., LABOSKY P.A., SHIOTA C., OKUYAMA S., IMAGAWA Y., FOGO A., NIIMURA F., ICHIKAWA I., HOGAN B.L., INAGAMI T. Effects on blood pressure and exploratory behaviour of mice lacking angiotensin II type-2 receptor. Nature. 1995;377:748–750. doi: 10.1038/377748a0. [DOI] [PubMed] [Google Scholar]
  20. IGLESIAS A.G., SUAREZ C., FEIERSTEIN C., DIAZ-TORGA G., BECU-VILLALOBOS D. Desensitization of angiotensin II: effect on [Ca2+]i, inositol triphosphate and prolactin in pituitary cells. Am. J. Physiol. Endocrinol. Metab. 2001;280:E462–E470. doi: 10.1152/ajpendo.2001.280.3.E462. [DOI] [PubMed] [Google Scholar]
  21. ITO M., OLIVERIO M.I., MANNON P.J., BEST C.F., MAEDA N., SMITHIES O., COFFMAN T.M. Regulation of blood pressure by the type 1A angiotensin II receptor gene. Proc. Natl. Acad. Sci. U.S.A. 1995;92:3521–3525. doi: 10.1073/pnas.92.8.3521. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. IWAI N., INAGAMI T. Identification of two subtypes in the rat type I angiotensin II receptor. FEBS Lett. 1992;298:257–260. doi: 10.1016/0014-5793(92)80071-n. [DOI] [PubMed] [Google Scholar]
  23. JIN X.Q., FUKUDA N., SU J.Z., LAI Y.M., SUZUKI R., TAHIRA Y., TAKAGI H., IKEDA Y., KANMATSUSE K., MIYAZAKI H. Angiotensin II type 2 receptor gene transfer downregulates angiotensin II type 1a receptor in vascular smooth muscle cells. Hypertension. 2002;39:1021–1027. doi: 10.1161/01.hyp.0000016179.52601.b4. [DOI] [PubMed] [Google Scholar]
  24. KATADA J., MAJIMA M. AT(2) receptor-dependent vasodilation is mediated by activation of vascular kinin generation under flow conditions. Br. J. Pharmacol. 2002;136:484–491. doi: 10.1038/sj.bjp.0704731. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. LEVY B.I., BENESSIANO J., HENRION D., CAPUTO L., HEYMES C., DURIEZ M., POITEVIN P., SAMUEL J.L. Chronic blockade of AT2-subtype receptors prevents the effect of angiotensin II on the rat vascular structure. J. Clin. Invest. 1996;98:418–425. doi: 10.1172/JCI118807. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. LI X.C., WIDDOP R.E. AT2 receptor-mediated vasodilatation is unmasked by AT1 receptor blockade in conscious SHR. Br. J. Pharmacol. 2004;142:821–830. doi: 10.1038/sj.bjp.0705838. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. MASAKI H., KURIHARA T., YAMAKI A., INOMATA N., NOZAWA Y., MORI Y., MURASAWA S., KIZIMA K., MARUYAMA K., HORIUCHI M., DZAU V.J., TAKAHASHI H., IWASAKA T., INADA M., MATSUBARA H. Cardiac-specific overexpression of angiotensin II AT2 receptor causes attenuated response to AT1 receptor-mediated pressor and chronotropic effects. J. Clin. Invest. 1998;101:527–535. doi: 10.1172/JCI1885. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. MUKOYAMA M., NAKAJIMA M., HORIUCHI M., SASAMURA H., PRATT R.E., DZAU V.J. Expression cloning of type 2 angiotensin II receptor reveals a unique class of seven-transmembrane receptors. J. Biol. Chem. 1993;268:24539–24542. [PubMed] [Google Scholar]
  29. MULLER C., ENDLICH K., HELWIG J.J. AT2 antagonist-sensitive potentiation of angiotensin II-induced constriction by NO blockade and its dependence on endothelium and P450 eicosanoids in rat renal vasculature. Br. J. Pharmacol. 1998;124:946–952. doi: 10.1038/sj.bjp.0701906. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. MUNZENMAIER D.H., GREENE A.S. Opposing actions of angiotensin II on microvascular growth and arterial blood pressure. Hypertension. 1996;27:760–765. doi: 10.1161/01.hyp.27.3.760. [DOI] [PubMed] [Google Scholar]
  31. NAKAJIMA M., HUTCHINSON H.G., FUJINAGA M., HAYASHIDA W., MORISHITA R., ZHANG L., HORIUCHI M., PRATT R.E., DZAU V.J. The angiotensin II type 2 (AT2) receptor antagonizes the growth effects of the AT1 receptor: gain-of-function study using gene transfer. Proc. Natl. Acad. Sci. U.S.A. 1995;92:10663–10667. doi: 10.1073/pnas.92.23.10663. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. OLIVERIO M.I., BEST C.F., KIM H.S., ARENDSHORST W.J., SMITHIES O., COFFMAN T.M. Angiotensin II responses in AT1A receptor-deficient mice: a role for AT1B receptors in blood pressure regulation. Am. J. Physiol. 1997;272:F515–F520. doi: 10.1152/ajprenal.1997.272.4.F515. [DOI] [PubMed] [Google Scholar]
  33. PÖRSTI I., HECKER M., BASSENGE E., BUSSE R. Dual action of angiotensin II on coronary resistance in the isolated perfused rabbit heart. Naunyn Schmiedebergs Arch Pharmacol. 1993;348:650–658. doi: 10.1007/BF00167243. [DOI] [PubMed] [Google Scholar]
  34. REAGAN L.P., YE X., MARETZSKI C.H., FLUHARTY S.J. Down-regulation of angiotensin II receptor subtypes and desensitization of cyclic GMP production in neuroblastoma N1E-115 cells. J. Neurochem. 1993;60:24–31. doi: 10.1111/j.1471-4159.1993.tb05818.x. [DOI] [PubMed] [Google Scholar]
  35. RYAN M.J., DIDION S.P., MATHUR S., FARACI F.M., SIGMUND C.D. Angiotensin II-induced vascular dysfunction is mediated by the AT1A receptor in mice. Hypertension. 2004;43:1074–1079. doi: 10.1161/01.HYP.0000123074.89717.3d. [DOI] [PubMed] [Google Scholar]
  36. SCHNEIDER M.D., LORELL B.H. AT(2), judgment day: which angiotensin receptor is the culprit in cardiac hypertrophy. Circulation. 2001;104:247–248. doi: 10.1161/01.cir.104.3.247. [DOI] [PubMed] [Google Scholar]
  37. SCHUIJT M.P., BASDEW M., VAN VEGHEL R., DE VRIES R., SAXENA P.R., SCHOEMAKER R.G., DANSER A.H.J. AT(2) receptor-mediated vasodilation in the heart: effect of myocardial infarction. Am. J. Physiol. Heart Circ. Physiol. 2001;281:H2590–H2596. doi: 10.1152/ajpheart.2001.281.6.H2590. [DOI] [PubMed] [Google Scholar]
  38. SCHUIJT M.P., DE VRIES R., SAXENA P.R., SCHALEKAMP M.A.D.H., DANSER A.H.J. Vasoconstriction is determined by interstitial rather than circulating angiotensin II. Br. J. Pharmacol. 2002;135:275–283. doi: 10.1038/sj.bjp.0704452. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. SIRAGY H.M., CAREY R.M. The subtype 2 (AT2) angiotensin receptor mediates renal production of nitric oxide in conscious rats. J. Clin. Invest. 1997;100:264–269. doi: 10.1172/JCI119531. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. SIRAGY H.M., INAGAMI T., ICHIKI T., CAREY R.M. Sustained hypersensitivity to angiotensin II and its mechanism in mice lacking the subtype-2 (AT2) angiotensin receptor. Proc. Natl. Acad. Sci. U.S.A. 1999;96:6506–6510. doi: 10.1073/pnas.96.11.6506. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. STOLL M., STECKELINGS U.M., PAUL M., BOTTARI S.P., METZGER R., UNGER T. The angiotensin AT2-receptor mediates inhibition of cell proliferation in coronary endothelial cells. J. Clin. Invest. 1995;95:651–657. doi: 10.1172/JCI117710. [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. SUTHERLAND F.J., SHATTOCK M.J., BAKER K.E., HEARSE D.J. Mouse isolated perfused heart: characteristics and cautions. Clin. Exp. Pharmacol. Physiol. 2003;30:867–878. doi: 10.1046/j.1440-1681.2003.03925.x. [DOI] [PubMed] [Google Scholar]
  43. TANAKA M., TSUCHIDA S., IMAI T., FUJII N., MIYAZAKI H., ICHIKI T., NARUSE M., INAGAMI T. Vascular response to angiotensin II is exaggerated through an upregulation of AT1 receptor in AT2 knockout mice. Biochem. Biophys. Res. Commun. 1999;258:194–198. doi: 10.1006/bbrc.1999.0500. [DOI] [PubMed] [Google Scholar]
  44. TOM B., GARRELDS I.M., SCALBERT E., STEGMANN A.P., BOOMSMA F., SAXENA P.R., DANSER A.H.J. ACE-versus chymase-dependent angiotensin II generation in human coronary arteries: a matter of efficiency. Arterioscler. Thromb. Vasc. Biol. 2003;23:251–256. doi: 10.1161/01.atv.0000051875.41849.25. [DOI] [PubMed] [Google Scholar]
  45. TSUTSUMI Y., MATSUBARA H., MASAKI H., KURIHARA H., MURASAWA S., TAKAI S., MIYAZAKI M., NOZAWA Y., OZONO R., NAKAGAWA K., MIWA T., KAWADA N., MORI Y., SHIBASAKI Y., TANAKA Y., FUJIYAMA S., KOYAMA Y., FUJIYAMA A., TAKAHASHI H., IWASAKA T. Angiotensin II type 2 receptor overexpression activates the vascular kinin system and causes vasodilation. J. Clin. Invest. 1999;104:925–935. doi: 10.1172/JCI7886. [DOI] [PMC free article] [PubMed] [Google Scholar]
  46. UTSUNOMIYA H., NAKAMURA M., KAKUDO K., INAGAMI T., TAMURA M. Angiotensin II AT2 receptor localization in cardiovascular tissues by its antibody developed in AT2 gene-deleted mice. Regul Pept. 2005;126:155–161. doi: 10.1016/j.regpep.2004.09.004. [DOI] [PubMed] [Google Scholar]
  47. VAN KATS J.P., DANSER A.H.J., VAN MEEGEN J.R., SASSEN L.M.A., VERDOUW P.D., SCHALEKAMP M.A.D.H. Angiotensin production by the heart: a quantitative study in pigs with the use of radiolabeled angiotensin infusions. Circulation. 1998;98:73–81. doi: 10.1161/01.cir.98.1.73. [DOI] [PubMed] [Google Scholar]
  48. VAN KESTEREN C.A.M., VAN HEUGTEN H.A.A., LAMERS J.M.J., SAXENA P.R., SCHALEKAMP M.A.D.H., DANSER A.H.J. Angiotensin II-mediated growth and antigrowth effects in cultured neonatal rat cardiac myocytes and fibroblasts. J. Mol. Cell Cardiol. 1997;29:2147–2157. doi: 10.1006/jmcc.1997.0448. [DOI] [PubMed] [Google Scholar]
  49. WANG Q.D., TOKUNO S., VALEN G., SJOQUIST P.O., THOREN P. Cyclic fluctuations in the cardiac performance of the isolated Langendorff-perfused mouse heart: pyruvate abolishes the fluctuations and has an anti-ischaemic effect. Acta Physiol. Scand. 2002;175:279–287. doi: 10.1046/j.1365-201X.2002.01003.x. [DOI] [PubMed] [Google Scholar]
  50. WIDDOP R.E., JONES E.S., HANNAN R.E., GASPARI T.A. Angiotensin AT2 receptors: cardiovascular hope or hype. Br. J. Pharmacol. 2003;140:809–824. doi: 10.1038/sj.bjp.0705448. [DOI] [PMC free article] [PubMed] [Google Scholar]
  51. WIDDOP R.E., MATROUGUI K., LEVY B.I., HENRION D. AT2 receptor-mediated relaxation is preserved after long-term AT1 receptor blockade. Hypertension. 2002;40:516–520. doi: 10.1161/01.hyp.0000033224.99806.8a. [DOI] [PubMed] [Google Scholar]
  52. YANG Z., BOVE C.M., FRENCH B.A., EPSTEIN F.H., BERR S.S., DIMARIA J.M., GIBSON J.J., CAREY R.M., KRAMER C.M. Angiotensin II type 2 receptor overexpression preserves left ventricular function after myocardial infarction. Circulation. 2002;106:106–111. doi: 10.1161/01.cir.0000020014.14176.6d. [DOI] [PubMed] [Google Scholar]
  53. YEE D.K., HEERDING J.N., KRICHAVSKY M.Z., FLUHARTY S.J. Role of the amino terminus in ligand binding for the angiotensin II type 2 receptor. Brain Res. Mol. Brain Res. 1998;57:325–329. doi: 10.1016/s0169-328x(98)00104-1. [DOI] [PubMed] [Google Scholar]
  54. YOU D., LOUFRANI L., BARON C., LEVY B.I., WIDDOP R.E., HENRION D. High blood pressure reduction reverses angiotensin II type 2 receptor-mediated vasoconstriction into vasodilation in spontaneously hypertensive rats. Circulation. 2005;111:1006–1011. doi: 10.1161/01.CIR.0000156503.62815.48. [DOI] [PMC free article] [PubMed] [Google Scholar]
  55. ZHANG C., HEIN T.W., WANG W., KUO L. Divergent roles of angiotensin II AT1 and AT2 receptors in modulating coronary microvascular function. Circ. Res. 2003;92:322–329. doi: 10.1161/01.res.0000056759.53828.2c. [DOI] [PubMed] [Google Scholar]

Articles from British Journal of Pharmacology are provided here courtesy of The British Pharmacological Society

RESOURCES