Cortisol feedback on ovine fetal ACTH secretion during the last fifth of gestation

Abstract

This study investigates the development of the feedback relationship between cortisol and ACTH in ovine fetuses at 117-119 (n = 5), 130-134 (n = 4) and 140-143 (n = 6) days of gestation. During the last 2 h of a 24 h cortisol (100 jig h-1) or saline (0-19 mL h-1) infusion, the fetal ACTH response to bolus oCRH injection (10 ng) was tested after the collection of basal ACTH and cortisol samples. Basal ACTH concentrations in un-infused or saline-infused fetuses were observed to progessively increase after 117-119 days of gestation. In contrast, a prepartum increase in cortisol concentrations could not be detected until after 130-133 days. Cortisol infusion significantly inhibited basal ACTH va..