Effect of the specific angiotensin antagonist (Sar1) (Ala8) angiotensin II on blood pressure and the renin-angiotensin system in the conscious pregnant ewe and fetus

Abstract

A direct relationship was found between maternal diastolic blood pressure and simultaneously measured angiotensin II (AII) levels (P < 0.001) in chronically cannulated pregnant ewes. The infusion of Saralasin to the ewe resulted in a dose-dependent fall in blood pressure (P < 0.005), the magnitude of which was proportional to the initial AII levels (P < 0.025). Plasma renin and AII levels rose significantly during the infusion. No consistent fetal effects were seen. The infusion of normal saline had no effect on blood pressure or hormone levels. Thus it seems likely that the renin-angiotensin system is involved with the maintenance of normal blood pressure in the pregnant sheep. Fetal blood pressure either fell significantly or was unchanged following direct infusion of Saralasin. This may be related to development of the β-adrenergic nervous system. The renin-angiotensin system may be more important in cardiovascular homeostasis in the immature than in the adult animal.