Elevated peripheral concentrations of LH block ovulation and increase thecal and serum progesterone in the hamster.
Insertion of osmotic minipumps containing 1 mg ovine LH on Day 1 (oestrus) elevated circulating serum concentrations of LH, progesterone and androstenedione when compared with values at pro-oestrus. Ovulation was blocked for at least 2 days at which time there were twice the normal numbers of preovulatory follicles. Follicular and thecal progesterone production in vitro was elevated when compared with that in pro-oestrous controls. Follicular and thecal androstenedione production in vitro was lower than in controls even though serum concentrations of androstenedione were elevated; the higher androstenedione values may be due to the increase in number of preovulatory follicles when compared with pro-oestrous controls. Follicles from LH-treated hamsters aromatized androstenedione to oestradiol and follicular production of oestradiol was similar to that in pro-oestrous follicles despite low follicular androstenedione production in the LH-treated group. Treatment with 20 i.u. hCG on Days 4 or 6 after insertion of an LH osmotic minipump on Day 1 induced ovulation of approximately 30 ova, indicating that the blockade of ovulation was not due to atresia of the preovulatory follicles. Serum progesterone concentrations on Days 2, 4 and 6 in LH-treated hamsters were greater than 17 nmol/l, suggesting that the blockade of ovulation might have been due to prevention of the LH surge by high serum progesterone concentrations.
D000735:Androstenedione / Q000097:blood; D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D006224:Cricetinae; D004958:Estradiol / Q000096:biosynthesis; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood* / Q000494:pharmacology; D010060:Ovulation / Q000187:drug effects*; D011247:Pregnancy; D011359:Proestrus; D011374:Progesterone / Q000097:blood / Q000378:metabolism*; D013799:Theca Cells / Q000378:metabolism*
D006063:Chorionic Gonadotropin; D000735:Androstenedione; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone