PATTERNS OF CIRCULATING OESTRONE, OESTRADIOL-17β AND PROGESTERONE DURING PREGNANCY IN THE RHESUS MONKEY

Abstract

ABSTRACT The maternal peripheral plasma levels of oestrone (E1)*, oestradiol-17β (E2) and progesterone (P) were determined by RIA during pregnancy in 8 rhesus monkeys (Macaca mulatta). Of special interest were the time courses and the inter-relationships of these steroids during the first month of pregnancy and during the pre- and post-parturient periods. A significant increase in the plasma levels of E1 and E2 occurred at the end of the fertile cycle and lasted for several days and again during the last week before parturition. The plasma levels of E1 and E2 fell dramatically after parturition and remained low during the immediate post-partum period. Two surges in the progesterone levels in plasma occurred at the end of the third week of the fertile cycle and between day 34 and 46 after the onset of menstruation. The progesterone levels in plasma during the remaining gestational period varied widely but a significant increase was found during the days before parturition. A decrease in the plasma levels of P was observed after parturition but the levels of P did not reach follicular phase levels during the post-partum period studied. The possibility of oestrogen secretion from follicles stimulated by chorionic gonadotrophins is discussed as well as the release of prostaglandins by oestrogen before parturition.