title: Developmental changes in pituitary responsiveness to luteinizing hormone-releasing hormone (LHRH) in the female rat: ovarian-adrenal influence during the infantile period.
abstract: Pituitary LH and FSH repsonses to synthetic LHRH as estimated by increases in plasma FSH and LH 15 and 45 min following its iv injection were enhanced during the first 2 weeks of life, reaching a maximum around day 10-15 and declining thereafter. No AM.-PM. variations in pituitary responsiveness were observed at any age studied. The increased pituitary response found in infantile rats did not appear to be caused by a slower rate of disappearance of LHRH in blood of the younger animals. Ovariectomy-adrenalectomy. (Ovx-Adrx) or Ovx at day 10, but not Adrx alone, resulted in elevated LH and FSH levels 5 days later and almost complete obliteration of the FSH response to LHRH. The LH response was not altered. Treatment with 5alha-dihydrotestosterone (DHT) but not with estradiol benzoate (EB) or testosterone propionate (TP) suppressed the post-Ovx-Adrx rise in plasma LH and FSH. Progesterone (P) potentiated the effect of DHT. Restoration of basal plasma LH and FSH levels (by DHT and/or P) restored FSH responsiveness to exogenous LHRH. EB and TP were ineffective. The LH response was slightly depressed by EB + DHT. It is concluded that the elevated plasma FSH levels in the infantile female rat may be due at least in part to a high degree of pituitary responsiveness to LHRH and/or FSH-RF brought about by steroidal signal of ovarian origin. DHT and P appear to be the steroids responsible for such a stimulatory action.
mesh_terms: D000311:Adrenal Glands / Q000502:physiology*; D000315:Adrenalectomy; D000375:Aging; D000818:Animals; D002369:Castration; D002940:Circadian Rhythm; D013196:Dihydrotestosterone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood; D010053:Ovary / Q000502:physiology*; D010902:Pituitary Gland / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology; D051381:Rats; D013739:Testosterone / Q000494:pharmacology
chemical_list: D013196:Dihydrotestosterone; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone