Restriction of placental and fetal growth in sheep alters fetal blood pressure responses to angiotensin II and captopril

1. We have measured arterial blood pressure between 115 and 145 days gestat ion in normally grown fetal sheep (control group; n = 16) and in fetal shee p in which growth was restricted by experimental restriction of placental g rowth and development (PR group; n = 13). There was no significant differen ce in the mean gestational arterial blood pressure between the PR (42.7 +/- 2.6 mmHg) and control groups (37.7 +/- 2.3 mmHg). Mean arterial blood pres sure and arterial P-O2 were significantly correlated in control animals (r = 0.53, P < 0.05, n = 16), but not in the PR, group. 2. There were no changes in mean arterial blood pressure in either the PR o r control groups in response to captopril (7.5 mu g captopril min(-1); PR g roup n = 7, control group n = 6) between 115 and 125 days gestation. After 135 days gestation, there was a significant decrease (P < 0.05) in the feta l arterial blood pressure in the PR group but not in the control group duri ng the captopril infusion (15 mu g captopril min(-1); PR group n = 7, contr ol group n = 6). 3. There was a significant effect (F = 14.75; P < 0.001) of increasing dose s of angiotensin II on fetal diastolic blood pressure in the PR and control groups. The effects of angiotensin II n ere different (F = 8.67; P < 0.05) in the PR and control groups at both gestational age ranges. 4. These data indicate that arterial blood pressure may be maintained by di fferent mechanisms in growth restricted fetuses and normally grown counterp arts and suggests a role for the fetal renin-angiotensin system in the main tenance of blood pressure in growth restricted fetuses.