Studies on the effects of angiotensin II on human chorionic plate arteries and their modification by a calcium antagonist, nitrendipine.

1 Six-point concentration-response curves were initially established for the contractile effect of angiotensin II (AII), at final concentrations of 10(-11) to 10(-6) M, on helically-cut strips of human chorionic plate arteries. The strips were then randomly allocated to one of four treatment groups: a control group and three treatment groups (n = 10 in each group) which were exposed to carrier or nitrendipine 10(-11), 10(-10) or 10(-9) M final concentration respectively, before the establishment of second concentration-response curves. 2 The initial responses of the tissues to AII were very similar in the four treatment groups with median EC50s ranging between 2.51 X 10(-10) and 4.04 X 10(-10) M (P greater than 0.8). The addition of nitrendipine was associated with significant (P less than 0.005) dose-related inhibition of AII-induced contractions. The median EC50 of the control group during the second half of the experiment was 1.77 X 10(-7) M, while that of the 10(-11) M nitrendipine treatment group was 2.16 X 10(-7) M. The EC50 for the other treatment groups could not be calculated from the curves due to the markedly blunted responses. 3 It is thus suggested that nitrendipine might be effective in vivo in the relief of vasospasm of the placental vascular system in pregnancy-induced hypertension.