title: Conversion of progesterone to 5 alpha- and 5 beta-reduced metabolites in the hen and its potential role in the induction of the preovulatory release of luteinizing hormone.
abstract: In the laying hen, progesterone was shown to be converted in vitro in the pituitary gland and the hypothalamus to 5 beta-pregnane-3,20-dione (5 beta-pregnane-3 alpha-ol-20-one (5 beta,3 alpha-ol) and 5 alpha-pregnane-3,20-dione (5 alpha-DHP) and in the hyperstriatum dorsale to 5 beta-DHP and 5 beta,3 alpha-ol. The conversion of progesterone to 5 beta-reduced metabolites was greater in the hyperstriatum dorsale than in the hypothalamus (P < 0.001) and greater in the hypothalamus than in the pituitary gland (P < 0.01). The conversion of progesterone to 5 beta-reduced metabolites was greater than its conversion to 5 alpha-DHP in the pituitary gland (P < 0.01) and the hypothalamus (P < 0.001). The possibility was investigated that 5 alpha-DHP and 5 beta-DHP may act as metabolic intermediaries in the mechanism by which progesterone exerts a positive feedback effect on LH release. Progesterone, 5 alpha-DHP and 5 beta-DHP were injected into laying hens at doses of 0.05, 0.25 and 1.25 mg/kg and the changes in the concentration of plasma LH were followed for 4 h thereafter. Secretion of LH was stimulated after treatment with progesterone or 5 alpha-DHP but not 5 beta-DHP. Progesterone stimulated Lh release more effectively than did 5 alpha-DHP, since an increase in the concentration of plasma LH was observed after 0.25 mg progesterone/kg but not after the same dose of 5 alpha-DHP. It was concluded that in the hen 5 alpa-DHP is unlikely to play a role in the induction of the preovulatory release of LH.
mesh_terms: D000818:Animals; D002645:Chickens; D003342:Corpus Striatum / Q000378:metabolism*; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000378:metabolism*; D010058:Oviposition; D010902:Pituitary Gland / Q000378:metabolism; D011277:Pregnanediones / Q000378:metabolism; D011280:Pregnanolone / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism* / Q000494:pharmacology; D012636:Secretory Rate / Q000187:drug effects
chemical_list: D011277:Pregnanediones; D011374:Progesterone; D007986:Luteinizing Hormone; D011280:Pregnanolone