Porcine Fetal and Maternal Adrenocorticotropic Hormone and Corticosteroid Concentrations during Gestation and their Relation to Fetal Size1

Abstract

A study was conducted to characterize fetal plasma ACTH and corticosteroid concentrations during porcine gestation and to relate plasma corticosteroids to fetal size. Samples were taken in white crossbred pigs at 50, 75, and 100 days of gestation and in Chinese Meishan pigs at Day 75. Fetuses developed in either "crowded" or "roomy" uterine environments after maternal uterine ligation, and all fluid samples were obtained during surgery. Fetal arterial cortisol decreased by 30% between Days 50 and 75 and then increased by 101% between 75 and 100 days. Concomitantly, fetal arterial ACTH increased 4-fold between 50 and 75 days of gestation and 45% between 75 and 100 days. Fetal venous cortisol and ACTH (measured only on Days 75 and 100) concentrations were lower than arterial concentrations. Both amniotic and allantoic fluid cortisol concentrations paralleled those of arterial cortisol but were at least 4-fold less. The percentage of free cortisol on Days 75 and 100 was a constant 24%, whereas cortisol bound to corticosteroid-binding globulin was a constant 60% and albumin-bound cortisol was 16%. White crossbred fetal arterial cortisone concentrations were always lower than cortisol concentrations, did not differ between arterial and venous plasma, decreased 50% between 50 and 75 days, and did not change thereafter. Plasma cortisol concentrations in Chinese Meishan fetuses were 30% greater than in white crossbred fetuses of the same age, but plasma ACTH and cortisone did not differ between breeds. Analysis of covariance indicated a negative regression of fetal weight and fetal length on arterial cortisol in white crossbred fetuses only at Day 100, and at Day 75 in Meishan fetuses. Under the specific conditions of this experimental model, these data demonstrate prenatal developmental changes in plasma ACTH and corticosteroids, indicate breed differences in such development, and suggest that a negative relationship exists between endogenous cortisol concentrations and fetal size at specific gestational ages.