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

Abstract

1 We have measured arterial blood pressure between 115 and 145 days gestation in normally grown fetal sheep (control group; n= 16) and in fetal sheep in which growth was restricted by experimental restriction of placental growth and development (PR group; n= 13). There was no significant difference 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 pressure and arterial P${}_{\text{O}{}_{\text{2}}}$ 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 or control groups in response to captopril (7.5 μg captopril min⁻¹; PR group 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 fetal arterial blood pressure in the PR group but not in the control group during the captopril infusion (15 μg captopril min⁻¹; PR group n= 7, control group n= 6). 3 There was a significant effect (F= 14.75; P < 0.001) of increasing doses of angiotensin II on fetal diastolic blood pressure in the PR and control groups. The effects of angiotensin II were 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 different mechanisms in growth restricted fetuses and normally grown counterparts and suggests a role for the fetal renin-angiotensin system in the maintenance of blood pressure in growth restricted fetuses.