In vitro effects of luteinizing hormone on induced atretic graafian follicles in the hamster.

Abstract

A synchronous population of atretic follicles was produced in hypophysectomized hamsters on the day of ovulation (Day 1) by injecting them immediately s.c. with pregnant mare's serum (PMS) followed by an i.p. injection of PMS-antiserum at 0900 h on Day 4. At various times thereafter isolated follicles were exposed in vitro to different doses of ovine luteinizing hormone (LH) (0 to 200 ng) and incubated for 1 h. Cyclic AMP (cAMP), estradiol (E2), testosterone equivalent (T), 17 alpha-hydroxyprogesterone (17-OH-P) and progesterone (P) were then measured. At 0900 h of Day 4, nonatretic follicles (not injected with PMS-antiserum) showed the highest level of cAMP, P and 17-OH-P in response to stimulation by 7 and 200 ng of LH. E2 and T were lowest in the groups incubated with no LH or with 200 ng/ml of LH and highest when stimulated by 7 ng. Atretic follicles showed a graded response to LH depending on the degree of atresia. By 12 h following injection of anti-PMS, none of the doses of LH produced significant increases in E2 or T; however, 200 ng of LH stimulated significant increases in P (1 ng increase) and 17-OH-P (564 pg increase) and increased cAMP above control levels (7.3 +/- 1.6 pmol vs. 2.6 +/- 0.2 pmol, respectively). By 24 h, with 200 ng LH, follicular 17-OH-P declined to control levels present at Time zero, followed by a fall in P at 48 h and cAMP at 72 h. Cyclic AMP and steroid levels were directly influenced by the dose of LH and the degree of atresia (P less than 0.0001). These studies indicate that with this model atretic follicles rapidly lose their ability to synthesize E2 and T while production of 17-OH-P, P and cAMP declines more slowly as atresia advances. Based on previous studies of others we postulate that the early breakdown of the granulosa may cause the initial drop in E2 and T while the theca continues to produce 17-OH-P, P and cAMP until more advanced stages of atresia.