Selective release of follicle-stimulating hormone and luteinizing hormone by 5 alpha-dihydroprogesterone and 3 alpha, 5 alpha-tetrahydroprogesterone in pregnant mare's serum gonadotropin-primed immature rats exposed to constant light.
The effects of 5 alpha-dihydroprogesterone (5 alpha-DHP) and 3 alpha, 5 alpha-tetrahydroprogesterone (3 alpha, 5 alpha-THP) on follicle-stimulating hormone (FSH) and luteinizing hormone (LH) release were examined in the pregnant mare's serum gonadotropin (PMSG)-primed immature female rat (8 IU PMSG at 28 days of age) maintained in constant light. Control rats kept in 14L:10D conditions exhibited proestrous-like surges of LH and FSH release with peak levels attained at 1800 h on the second day after PMSG treatment. In rats exposed to constant light, the PMSG-induced surges of LH and FSH were not only delayed until 1000 h on the third day after PMSG, resulting in a delay in ovulation, but were also significantly attenuated when compared to the gonadotropin surges that occurred on Day 2 in rats kept under normal light-dark conditions. The administration of 5 alpha-DHP significantly enhanced the release of FSH at 1000 h on Day 3 when compared to constant light-exposed controls, but had no effect on LH. Treatment with 3 alpha, 5 alpha-THP selectively potentiated the release of LH at 1000 h on Day 3 and had an attenuating effect on FSH release on Days 2 and 3. These observations confirm earlier findings in the immature ovariectomized estrogen-primed rat and suggest that 5 alpha-DHP and 3 alpha, 5 alpha-THP may have significant roles in the regulation of FSH and LH secretion.
D043582:5-alpha-Dihydroprogesterone; D000818:Animals; D002940:Circadian Rhythm; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D006064:Gonadotropins, Equine / Q000494:pharmacology*; D008027:Light; D007986:Luteinizing Hormone / Q000378:metabolism*; D010060:Ovulation / Q000187:drug effects / Q000528:radiation effects; D011277:Pregnanediones / Q000494:pharmacology*; D011278:Pregnanes / Q000494:pharmacology*; D011280:Pregnanolone / Q000494:pharmacology*; D051381:Rats
D006064:Gonadotropins, Equine; D011277:Pregnanediones; D011278:Pregnanes; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D043582:5-alpha-Dihydroprogesterone; D011280:Pregnanolone