title: Prolactin (PRL), follicle-stimulating hormone, and luteinizing hormone are regulators of testicular PRL receptors in golden hamsters.
abstract: The ability of PRL, FSH, and LH to regulate testicular PRL receptors in golden hamsters was evaluated using a variety of experimental protocols. Exposure to a photoperiod of 5 h of light and 19 h of darkness (5L:19D) for 11 weeks precipitated a 94% reduction in content (femtomoles per testes) of testicular PRL receptors and, concomitantly, a decrease (P less than 0.05) in plasma PRL, but not LH or FSH. One pituitary gland under the kidney capsule in 5L:19D-housed hamsters increased (P less than 0.05) both the concentration (femtomoles per mg protein) and content of PRL receptors, as well as those of plasma PRL and FSH. Similar treatment in 14L:10D-housed hamsters produced comparable changes in plasma PRL and FSH without affecting PRL receptors. Injections of L-dopa for 7 days into hamsters housed in 5L:19D for 11 weeks significantly elevated serum FSH concentrations, had no measurable effect on serum PRL and LH, and induced a greater than 2-fold increase in PRL receptor levels. In a separate study, hamsters housed in 5L:19D for 12 weeks were injected for 3 days with 250 microgram ovine (o) PRL, 25 microgram oLH, or 5 microgram oFSH, and results were compared with vehicle-injected, 5L:19D- and 14L:10D-housed controls. Injections of oPRL and oLH increased (P less than 0.05) PRL receptor concentration and content, with PRL being more efficacious. No anti-oPRL antibodies were produced by oPRL injections. In this study, injections of oFSH were without effect on PRL receptors. To ascertain the effects of each hormone in the absence of other trophic influences, experiments were conducted in hypophysectomized hamsters injected daily for 3 days (2-4 days posthypophysectomy) with one of the following: 5 or 25 microgram oLH; 10, 50, or 250 microgram oPRL; or 1 or 5 microgram oFSH. Hypophysectomy reduced the concentration and content of PRL receptors by 85%, and treatment with 50 or 250 microgram oPRL increased (P less than 0.05) these low levels almost 3-fold. Again, no anti-oPRL antibodies were induced. Injection of 5 microgram oLH or 25 microgram oFSH also induced increases (P less than 0.05) in PRL receptors. Hypophysectomy reduced basal and hCG-stimulated in vitro testicular testosterone production (nanograms per testes/4 h) to levels less than 20% of control values. None of the hormonal treatments affected (P less than 0.05) basal testosterone production in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)
mesh_terms: D000818:Animals; D006224:Cricetinae; D005640:Follicle Stimulating Hormone / Q000494:pharmacology / Q000502:physiology*; D007016:Hypophysectomy; D007700:Kinetics; D007980:Levodopa / Q000494:pharmacology; D008027:Light; D007986:Luteinizing Hormone / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D008647:Mesocricetus; D009929:Organ Size; D010507:Periodicity; D010903:Pituitary Gland, Anterior / Q000502:physiology / Q000637:transplantation; D011388:Prolactin / Q000494:pharmacology / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D011981:Receptors, Prolactin; D013737:Testis / Q000033:anatomy & histology / Q000378:metabolism* / Q000528:radiation effects; D013739:Testosterone / Q000096:biosynthesis
chemical_list: D011956:Receptors, Cell Surface; D011981:Receptors, Prolactin; D013739:Testosterone; D007980:Levodopa; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone