Inhibition of progesterone secretion by a 3β-hydroxysteroid dehydrogenase inhibitor in pregnant goats

ABSTRACT Epostane, an inhibitor of 3β-hydroxysteroid dehydrogenase, was administered to goats in late pregnancy in the presence or absence of concurrent treatment with prostaglandin synthetase inhibitors (indomethacin and diclofenac sodium) and the effect on steroidogenesis in the corpus luteum and adrenal cortex determined by measurement of peripheral concentrations of progesterone and cortisol respectively. Concentrations of both steroids were reduced to about 20% of pretreatment levels within 6 h of epostane administration. Cortisol concentrations subsequently increased about 24 h after epostane administration and returned to and exceeded pretreatment values, but progesterone concentrations remained suppressed until premature delivery, which occurred in all animals 44 ± 2 h (mean ± s.e.m.) after epostane administration. However, combined administration of epostane and prostaglandin synthetase inhibitor prevented the onset of labour in the majority of animals, but progesterone secretion in animals receiving this combined treatment did not differ from that in animals given epostane alone. It is concluded that progesterone withdrawal is an important component of the mechanisms which initiate parturition in the goat and that increased prostaglandin synthesis is essential for delivery in this species, but perhaps not for luteolysis. J. Endocr. (1987) 113, 489–493