Serum Progesterone and Fetal Morphology Following Ovariectomy and Adrenalectomy in the Pregnant Rat

Abstract

Morphological degeneration of the fetus and associated embryological tissues was temporarily correlated with a precipitous decline in serum progesterone concentrations following ovariectomy (OVX) and ovariectomy combined with adrenalectomy (OVX, ADX) on Day 11 of pregnancy in the rat. Definitive signs of morphological change were seen upon histological examination 12 h following OVX and OVX/ADX when serum progesterone concentrations were at base levels. A greater degree of degeneration was observed in the OVX/ADX animals in contrast to OVX animals. Progesterone administration of 4.0 mg/day to Day 14 maintained pregnancy and prevented morphological degeneration. OVX rats as compared to OVX/ADX animals showed consistently higher serum progesterone levels throughout the 30 h experimental period following surgery as well as a serum progesterone peak at 2200 h which was not evidenced in the OVX/ADX animals. These observations support 1) a significant adrenal contribution to the serum progesterone pool and 2) the possibility of a diurnal rhythm in adrenal progesterone during pregnancy in the rat.