Angiotensin II has depressor effects in pregnant and nonpregnant women

Studies in anesthetized animals suggest that angiotensin II evokes a depressor as well as a pressor effect, which becomes evident on cessation of infusion. We have studied 18 nonpregnant and 8, 23, and 22 women in the first, second, and third trimesters of pregnancy to determine whether such an effect is present in conscious women, whether it is dose dependent, and whether it is influenced by pregnancy. Angiotensin II was infused intravenously in doubling concentrations at 10-minute intervals until a pressor effect of approximately 20 mm Hg was observed. The infusion was stopped, and blood pressure was monitored at 2-minute intervals for 30 minutes. There was a significant diastolic depressor effect after stopping angiotensin II in the nonpregnant women and those in the second and third trimesters of pregnancy. Individual women required differing doses of angiotensin II to evoke the standardized pressor response. It was thus possible to examine the depressor response in each group in relation to infused doses of angiotensin II. In nonpregnant women and in those in the second and third trimesters of pregnancy, the depressor response was dose dependent (P<.001). At any given dose, the depressor response deepened as pregnancy progressed (P<.001). Basal plasma prostacyclin concentrations rise in pregnancy, and angiotensin II can stimulate prostacyclin synthesis. This might mediate the depressor effect. In conclusion, the diminished pressor response to angiotensin II in normal pregnancy may be partly due to an increasing depressor effect of the hormone.