INTERLEUKIN-1-ALPHA INCREASES THECAL PROGESTERONE PRODUCTION OF PREOVULATORY FOLLICLES IN CYCLIC HAMSTERS

Adult cyclic hamsters were used to study the effects of interleukin-1α (IL-1α) on in vitro steroidogenesis in preovulatory follicles. IL-1α increased progesterone secretion by preovulatory follicles during a 24-h incubation in RPMI-1640 medium containing hCG (100 mIU/ml) (progesterone levels: 17.5 ± 2.2 vs. 10.6 ± 1.9 ng/follicle/ml, p < 0.05). IL-1α alone had no effect on follicular steroidogenesis. The source of increased progesterone secretion was the thecae (9.8 ± 1.0 vs. 5.8 ± 0.4 ng/2 thecae/ml, p < 0.01) and not the granulosa cells (6.6 ± 0.2 vs. 6.8 ± 0.5 ng/20,000 viable granulosa cells/ml). IL-1α also stimulated production of testosterone in thecae of preovulatory follicles. The follicular progesterone increase was dependent on the time of incubation and dose of IL-1α. IL-1α at 5-50 U/ml maximally stimulated progesterone production in the preovulatory follicles, and no significant effect of IL-1α was observed until the 12th hour of incubation. The effects of IL-1α on in vitro steroidogenesis in preantral follicles, experimentally induced atretic preovulatory follicles, and newly formed corpora lutea were examined. IL-1α in the presence of hCG also significantly increased progesterone secretion by atretic preovulatory follicles. In the incubation of preantral follicles or newly formed corpora lutea, however, IL-1α did not alter steroidogenesis. These results indicate that IL-1α stimulates progesterone secretion by preovulatory follicles and that the target tissue for this effect is the thecal layer. Moreover, the effect of IL-1α apparently depends on the stage of follicular development since preantral follicles do not respond to IL-1α.