FACTORS CONTRIBUTING TO THE FORMATION OF EXPERIMENTALLY-INDUCED OVARIAN CYSTS IN PREPUBERTAL GILTS

Manipulation of an ovary during the follicular phase in cycling gilts or prepubertal gilts treated with PMSG and hCG results in formation of cysts on manipulated ovaries and corpora lutea (CL) of normal appearance on nonmanipulated ovaries. In contrast, cysts did not form after manipulation in luteal phase gilts. In the present experiment, daily administration of 50 mg progesterone to prepubertal gilts treated with PMSG and hCG established luteal phase concentrations of progesterone but did not lessen the incidence of manipulated-induced cysts. Number of cysts formed was associated with the number of follicles greater-than-or-equal-to 5 mm at manipulation, which was inversely related to serum concentrations of progesterone. Number of receptors for LH/hCG in follicular tissues did not differ between manipulated and nonmanipulated ovaries but was greater in granulosa (P<.05) and theca (P<.08) from follicles with diameters greater-than-or-equal-to 7 mm compared to 5 and 6 mm. Contents of estradiol, androstenedione, testosterone, progesterone and prostaglandins E2 and F2alpha in follicular fluid, granulosa and theca were not different between follicles greater-than-or-equal-to 5 mm destined to form cysts or CL. Exogenous prostaglandin E2 or F2alpha given during follicular development failed to induce cysts. Profiles of progesterone and estradiol in peripheral serum and duration of luteal phase concentrations of progesterone were not different for gilts with induced cysts and gilts with CL. In conclusion, manipulation of follicles resulted in a failure to ovulate. Subsequent formation of cysts did not result from or result in a loss of steroidogenic function or the ability to bind LH to follicular receptors. These results demonstrate that the mechanism for ovulation is independent of other follicular processes, since ovulation can be disrupted without altering follicular steriodogenesis or subsequent luteinization.