Developmental changes in steroidogenesis by equine preovulatory follicles: effects of equine LH, FSH, and CG

Endocrinology
J SiroisJ E Fortune

Abstract

Ovulation in mares is preceded by a long and variable estrous period. The differentiation of equine preovulatory follicles with respect to steroidogenic capacity and responsiveness to equine gonadotropins was studied by culturing pieces of follicle wall (FW = theca + attached granulosa cells) from preovulatory follicles isolated during late diestrus (day 14 of cycle, n = 5 mares), early estrus (1st-2nd day of estrus, n = 6) or late estrus (4th or 5th day of estrus, n = 6). FW was cultured with or without equine LH, FSH, LH + FSH, or CG (10 or 100 ng/ml) and medium was collected and replaced at 3, 6, 12, 24, 48, and 72 h of culture. Follicular fluid from presumptive ovulatory follicles and medium from FW cultures were assayed for progesterone, androstenedione, and estradiol-17 beta. The cumulative secretion of all three steroids after 72 h of culture was significantly lower in FW isolated during late diestrus (P less than 0.05) as compared with early or late estrus. Maximal progesterone secretion was observed with FW from late estrus whereas maximal androstenedione and estradiol secretion in vitro occurred with FW from early estrus. In contrast to results obtained in vitro, concentrations of progesterone in follicular fluid were...Continue Reading

Citations

Aug 28, 2010·Reproduction, Fertility, and Development·C M ChecuraO J Ginther
Mar 27, 2002·The Journal of Veterinary Medical Science·Ana Y KojimaKunitada Sato

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