Induction of parturition in sheep by low dose intrafetal infusion of synthetic adrenocorticotropin-(1-24) at 120-130 days gestation.

Abstract

ACTH infusions into fetal sheep have been extensively used as a method of inducing premature parturition and the investigation of the associated endocrine and maturational changes in the fetus and ewe. Synthetic ACTH [ACTH-(1–24)] has been generally used in doses of 4–10 μg/h to induce parturition. These dose rates greatly exceed calculated endogenous fetal blood production rates for ACTH. The present study was designed to investigate the endocrine changes occurring in fetal and maternal ovine plasma during the induction of premature delivery with continuous infusion of a more physiological dose [1 μg ACTH-(1–24)/h]. The effect of ACTH-(1–24) infusions to the fetus at 120 or 130 days gestation were compared with appropriate gestational age controls. During ACTH-(1–24) infusion, the fetal plasma cortisol concentration in both age groups rose at similar rates. Furthermore, levels at delivery were equal to those observed in normal term fetuses. Where possible, three-parameter exponential curves were fitted t...