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. 2004 Oct 14;561(Pt 3):671–683. doi: 10.1113/jphysiol.2004.073098

Figure 2. Effect of angiotensin II on the contractility of pericytes located on freshly isolated retinal microvessels.

Figure 2

A, relationship between the concentration of angiotensin and the percentage of pericytes induced to contract. At angiotensin concentrations of ≥10 nm, the percentage of contracting pericytes was significantly (P < 0.001, Fisher's exact test) increased. The number of pericytes monitored by time-lapse photography was 292, 24, 31, 21, 23 and 193 for angiotensin concentrations of 0, 5, 10, 25, 50 and 500 nm, respectively. B, the contractile effect of angiotensin II and an AT1 receptor agonist under various conditions. The labelled columns indicate the groups in which the perfusate (solution A) was supplemented with angiotensin II (500 nm), L162313 (100 nm), BAPTA-AM (10 μm), nifedipine (10 μm) or chelerythrine (1 μm) or was modified by omitting CaCl2 and adding 3 mm EGTA. Compared with the angiotensin group, *P ≤ 0.005 (Fisher's exact test). The number of pericytes monitored by time-lapse photography was 193, 73, 41, 23, 73 and 68 for the angiotensin, L162313, BAPTA, calcium-free, nifedipine and chelerythrine groups, respectively. C, effect of 10 μm nifedipine and 1 μm chelerythrine on vasoconstriction induced by 500 nm angiotensin II. Compared with the control value, *P ≤ 0.005 (Student's paired t test). The vasoconstriction induced by angiotensin in the presence of nifedipine was significantly (P = 0.006) less than the constriction induced in the absence of this calcium channel inhibitor. The presence of chelerythrine did not significantly (P = 0.8) affect the magnitude of the angiotensin-induced vasoconstriction. Because exposure to either nifedipine or chelerythrine did not significantly (P > 0.1) affect lumen diameter, the control value shown is the mean diameter of microvessels exposed to solution A without (n = 12) or with nifedipine (n = 6) or chelerythrine (n = 6). The number of monitored lumens was 24, 12, 6 and 6 for the control, angiotensin, angiotensin/nifedipine and angiotensin/chelerythrine groups, respectively. Error bars show s.e.m.