Corticotropin-releasing factor-like immunoreactivity, arginine vasopressin-like immunoreactivity and ACTH-releasing bioactivity in hypothalamic tissue from fetal and neonatal sheep.

Abstract

Corticotropin-releasing factor-like immunoreactivity (CRF-LI), arginine vasopressin-like immunoreactivity (AVP-LI) and ACTH-releasing bioactivity of hypothalamic tissue from 63- to 143-day-old ovine fetuses and from 7- and 150-day-old lambs have been assessed. CRF-LI and AVP-LI contents and concentrations increased steadily between 63 and 138 days of gestation, decreased at day 143 then rose again in postpartum animals. In terms of concentration, the AVP-LI/CRF-LI ratio remained close to 5 between 63 and 123 days of intrauterine life, decreased steadily in late gestation down to 1.2 at day 143 increased again in lambs. The total hypothalamic ACTH-releasing bioactivity increased 26-fold between 63 and 138 days of gestation and remained constant until day 143. The highest values were observed in 150-day-old-lambs. These data support the view that AVP and oCRF1-41 might be important hypothalamic factors involved in the regulation of ACTH release by the pituitary gland of the sheep fetus. In addition, they suggest that AVP is more important in young fetuses and lambs than in prepartum animals.