Influences of Luteinizing Hormone Releasing Hormone, Hypophysectomy and Orchidectomy on the Differentiation of Luteinizing Hormone and Follicle- Stimulating Hormone Cells in an Ectopic Pituitary in the Hamster’

In these experiments we examined the effects of luteinizing hormone releasing hormone (LHRH) and gonadal and pituitary hormones on the appearance of luteinizing hormone (LH) and follicle-stimulating hormone (FSI-I) cells in ectopic pituitaries in the hamster. As a reference, we first determined the sequence of appearance of these hormones in perinatal animals using immuno-histochemical (IHC) and radioimmunoassay (RIA) procedures. Neither hormone could be detected in pituitaries at 13 days of gestation by either technique. Both hormones could be detected by IHC at 15 days of gestation using anti-rat LH S4, anti-rat LH3, anti-rat FSH S-7, and anti-rat FSI-Ia antisera. Il-IC and RIA revealed an increase in gonadotroph population and gonadotrophin content, respectively, between 5 and 12 days of postnatal life. By Day 8 a sex difference emerged with RIA so that by Day 12 both pituitary LH and FSH content were higher in females. In serum, only FSH was higher in females. To study the determinants of gonadotroph differentiation, fetal (Days 13-15 of gestation) or postnatal pituitaries (<3 days) were transplanted to a site remote from the hypothalamus (beneath the renal capsule) of hosts whose endocrine state could be manipulated easily (adult male ham