Cardiovascular and hypothalamic-pituitary-adrenal axis development in late gestation fetal sheep and young lambs following modest maternal nutrient restriction in early gestation

The effect of a 15% reduction in maternal nutrition for the first 70 days of gestation on cardiovascular and hypothalamic-pituitary-adrenal (HPA) axis responses to administration of corticotropin releasing hormone (CRH) + arginine vasopressin (AVP) was studied at 128 +/- 0.7 days gestation in fetal sheep and postnatally, at 85 +/- 4.5 days in young lambs. The effect on the fetal cardiovascular response to acute hypoxaemia was also examined, Under basal conditions, fetal heart rate (FHR) was reduced (P < 0.05) and basal femoral artery vascular resistance (FVR) was increased (P < 0.05) in fetuses of dietary-restricted (R) ewes compared with controls (C). Fetal mean arterial pressure (MAP) was similar in both groups. Femoral artery vascular resistance was also greater during hypoxaemia in R fetuses compared with C fetuses (P < 0.05), suggesting that chemoreflex mechanisms were augmented in the R group. The fetal ACTH response to CRH + AVP was similar in both groups. However, cortisol responses to CRH + AVP were smaller in R fetuses compared with C fetuses (P < 0.05). Postnatally, basal MAP (P < 0.05), and ACTH (P < 0.01) and cortisol (P < 0.001) responses were greater in R lambs compared with C lambs. It was concluded that modest maternal undernutrition during pregnancy alters development of the cardiovascular system, producing elevated blood pressure in postnatal life. Development of the HPA axis is also altered. with reduced activity during fetal life, but increased activity postnatally. The data suggest that the HPA axis may play a role in mediating the elevation of MAP in R lambs.