Secretion of inhibin A and inhibin B throughout pregnancy and the early postpartum period in chimpanzees

Plasma concentrations of inhibin A and inhibin B during pregnancy and early lactation in chimpanzees were determined by enzyme-linked immunosorbent as say (ELISA). Plasma samples were taken from five pregnant chimpanzees at 6- 9, 10, 20 and 25 weeks of pregnancy, and following parturition. Throughout pregnancy and the early postpartum period, circulating inhibin A and inhibi n B concentrations remained low, at similar levels to those during the norm al menstrual cycle in chimpanzees. Concentrations of inhibin A in the place ntal homogenate were high enough to be measured by the ELISA and by bioassa y, whereas circulating inhibin bioactivities in late pregnancy were too law to be measured. Plasma concentrations of FSH remained low with no signific ant changes throughout pregnancy and the postpartum period. Plasma concentr ations of oestradiol-17 beta and progesterone at 25 weeks of pregnancy were much higher than normal menstrual cycle levels. It was concluded that in c himpanzees the levels of circulating inhibin A and inhibin B remained low t hroughout pregnancy and the early postpartum period, and that the concentra tions of bioactive dimeric inhibin did not increase towards the end of preg nancy. The suppression of circulating FSH levels during pregnancy is sugges ted to be controlled by steroid hormones that increased significantly in la te pregnancy, and the present findings further suggest that the secretory p attern and role of inhibin during pregnancy in chimpanzees may be different from that in human and other primates.