STEROID REGULATION OF ESTROGEN AND PROGESTIN RECEPTOR MESSENGER-RIBONUCLEIC-ACID IN MONKEY HYPOTHALAMUS AND PITUITARY

The regulation of estrogen and progestin receptor (ER and PR, respecti vely) messenger RNA (mRNA) and protein by their cognate hormones was e xamined in the hypothalamus and pituitary of steroid-treated monkeys. Rhesus macaques (Macaca mulatta) were ovariectomized, hysterectomized (spayed), and implanted with SILASTIC brand capsules containing 17 bet a-estradiol (E) or progesterone (P). The spayed control group received empty capsules. The E-treated group received E-filled capsules for 28 days. The E+P-treated group received E-filled capsule for 28 days and then a P-filled capsule for the last 14 of the 28 days. Steroid regul ation of ER and PR mRNA levels in the hypothalamus and pituitary was e xamined with in situ hybridization. In the hypothalamus, ER and PR imm unodetectable proteins were also examined in nearby sections. In the p ituitary, mRNA levels were compared to previous ER and PR protein anal ysis of identically treated animals. E treatment induced PR mRNA in th e medial basal hypothalamus and pituitary. Supplemental P treatment ha d no effect on PR mRNA levels in the hypothalamus, but markedly reduce d PR mRNA in the pituitary. There was excellent agreement with PR prot ein detection by immunocytochemistry. E treatment had no effect on ER mRNA in the hypothalamus or pituitary. Supplemental P treatment decrea sed ER mRNA in the ventromedial nucleus, but not in the arcuate nucleu s or pituitary. There was agreement between ER mRNA and ER protein in these areas. In summary, there is cell-specific regulation of PR by P in the hypothalamus and pituitary, where P down-regulates PR in the pi tuitary without affecting ER. However, P has no significant effect on PR expression in the hypothalamus even though P decreases ER in the ve ntromedial nucleus. Although these observations suggest diverse cell-s pecific regulatory mechanisms, they are consistent with ER- and PR-med iated physiological events, such as PRL secretion and sexual behavior.