Abstract
1. Vascular smooth muscle cells were isolated from the portal vein and from pial vessels of the cow. They were voltage-clamped with a single patch electrode technique (whole cell recording) in order to analyse the effects of niguldipine on ionic membrane currents. Due to adsorption of niguldipine to plastic and glass, the effective concentrations are lower than the nominal concentrations by a factor of about 3. 2. Niguldipine reduced Ca-currents (ICa of the L-type, voltage operated) at nominal concentrations greater than 0.1 microM up to a complete block at 1 microM (50% block at 0.4 microM). Nominal concentrations between 50 and 200 nM facilitated ICa ('Ca-agonistic effect'). The Ca-agonistic effects of niguldipine showed modest use- but strong voltage-dependence. 3. Niguldipine increased the outward currents at nominal concentrations greater than 10 nM. The extra outward currents reversed at -85 mV, the result suggesting that niguldipine had increased potassium currents, IK. Maximal facilitation of IK by niguldipine was about 400% and was obtained at 1 microM, half-maximal facilitation was obtained with a nominal concentration of 20 nM. 4. Both reduction of ICa and facilitation of IK may contribute to vasodilatation by niguldipine. Due to its greater sensitivity, the effects on IK may dominate.
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- Allen S. L., Boyle J. P., Cortijo J., Foster R. W., Morgan G. P., Small R. C. Electrical and mechanical effects of BRL34915 in guinea-pig isolated trachealis. Br J Pharmacol. 1986 Oct;89(2):395–405. doi: 10.1111/j.1476-5381.1986.tb10273.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Benham C. D., Bolton T. B., Lang R. J., Takewaki T. Calcium-activated potassium channels in single smooth muscle cells of rabbit jejunum and guinea-pig mesenteric artery. J Physiol. 1986 Feb;371:45–67. doi: 10.1113/jphysiol.1986.sp015961. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Brown A. M., Kunze D. L., Yatani A. Dual effects of dihydropyridines on whole cell and unitary calcium currents in single ventricular cells of guinea-pig. J Physiol. 1986 Oct;379:495–514. doi: 10.1113/jphysiol.1986.sp016266. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Cerbai E., Klöckner U., Isenberg G. Ca-antagonistic effects of adenosine in guinea pig atrial cells. Am J Physiol. 1988 Oct;255(4 Pt 2):H872–H878. doi: 10.1152/ajpheart.1988.255.4.H872. [DOI] [PubMed] [Google Scholar]
- Ehara T., Daufmann R. The voltage- and time-dependent effects of (-)-verapamil on the slow inward current in isolated cat ventricular myocardium. J Pharmacol Exp Ther. 1978 Oct;207(1):49–55. [PubMed] [Google Scholar]
- Fischer G., Krumpl G., Mayer N., Schneider W., Raberger G. Antihypertensive effects of niguldipine-HCl (B 844-39), a new calcium antagonist in dogs. J Cardiovasc Pharmacol. 1987 Sep;10(3):268–273. doi: 10.1097/00005344-198709000-00003. [DOI] [PubMed] [Google Scholar]
- Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
- Hamilton T. C., Weir S. W., Weston A. H. Comparison of the effects of BRL 34915 and verapamil on electrical and mechanical activity in rat portal vein. Br J Pharmacol. 1986 May;88(1):103–111. doi: 10.1111/j.1476-5381.1986.tb09476.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hess P., Lansman J. B., Tsien R. W. Different modes of Ca channel gating behaviour favoured by dihydropyridine Ca agonists and antagonists. Nature. 1984 Oct 11;311(5986):538–544. doi: 10.1038/311538a0. [DOI] [PubMed] [Google Scholar]
- Klöckner U., Isenberg G. Action potentials and net membrane currents of isolated smooth muscle cells (urinary bladder of the guinea-pig). Pflugers Arch. 1985 Dec;405(4):329–339. doi: 10.1007/BF00595685. [DOI] [PubMed] [Google Scholar]
- Klöckner U., Isenberg G. Calcium currents of cesium loaded isolated smooth muscle cells (urinary bladder of the guinea pig). Pflugers Arch. 1985 Dec;405(4):340–348. doi: 10.1007/BF00595686. [DOI] [PubMed] [Google Scholar]
- Klöckner U., Isenberg G. Tiapamil reduces the calcium inward current of isolated smooth muscle cells. Dependence on holding potential and pulse frequency. Eur J Pharmacol. 1986 Aug 15;127(3):165–171. doi: 10.1016/0014-2999(86)90360-2. [DOI] [PubMed] [Google Scholar]
- Lee K. S., Tsien R. W. Mechanism of calcium channel blockade by verapamil, D600, diltiazem and nitrendipine in single dialysed heart cells. Nature. 1983 Apr 28;302(5911):790–794. doi: 10.1038/302790a0. [DOI] [PubMed] [Google Scholar]
- McDonald T. F., Pelzer D., Trautwein W. On the mechanism of slow calcium channel block in heart. Pflugers Arch. 1980 May;385(2):175–179. doi: 10.1007/BF00588699. [DOI] [PubMed] [Google Scholar]
- Sanguinetti M. C., Kass R. S. Voltage-dependent block of calcium channel current in the calf cardiac Purkinje fiber by dihydropyridine calcium channel antagonists. Circ Res. 1984 Sep;55(3):336–348. doi: 10.1161/01.res.55.3.336. [DOI] [PubMed] [Google Scholar]
- Thomas G., Gross R., Schramm M. Calcium channel modulation: ability to inhibit or promote calcium influx resides in the same dihydropyridine molecule. J Cardiovasc Pharmacol. 1984 Nov-Dec;6(6):1170–1176. [PubMed] [Google Scholar]
- Weir S. W., Weston A. H. Effect of apamin on responses to BRL 34915, nicorandil and other relaxants in the guinea-pig taenia caeci. Br J Pharmacol. 1986 May;88(1):113–120. doi: 10.1111/j.1476-5381.1986.tb09477.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Weir S. W., Weston A. H. The effects of BRL 34915 and nicorandil on electrical and mechanical activity and on 86Rb efflux in rat blood vessels. Br J Pharmacol. 1986 May;88(1):121–128. doi: 10.1111/j.1476-5381.1986.tb09478.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wilson D. L., Morimoto K., Tsuda Y., Brown A. M. Interaction between calcium ions and surface charge as it relates to calcium currents. J Membr Biol. 1983;72(1-2):117–130. doi: 10.1007/BF01870319. [DOI] [PubMed] [Google Scholar]