EFFECTS OF INTERLEUKIN-6 ON PROLIFERATION AND FOLLICLE-STIMULATING HORMONE-INDUCED ESTRADIOL PRODUCTION BY BOVINE GRANULOSA-CELLS IN-VITRO - DEPENDENCE ON SIZE OF FOLLICLE

The objective of the present studies was to determine the effect of IL -6 on proliferation and FSH-induced estrogen production by granulosa c ells from small (1-5 mm) and large (greater than or equal to 8 mm) bov ine follicles. FSH-induced estradiol production by granulosa cells fro m large follicles (expressed as pg estradiol/l0(5) cells/24 h) was not affected (p > 0.05) by 0.1, 1.0, or 10 ng/ml of interleukin (IL)-6, w hereas 30 and 100 ng/ml of IL-6 inhibited (p < 0.05) FSH-induced estra diol production by 32% in cells from large follicles. In comparison, a ll doses of IL-6 inhibited (p < 0.05) FSH-induced estradiol production in cultures of cells from small follicles; maximal inhibition was ach ieved (75% decrease) with greater than or equal to 10 ng/ml. IL-6 was also a more potent inhibitor of cell proliferation in cultures of cell s from small (55% inhibition) than from large (32% inhibition) follicl es. In summary, IL-6 has a more potent inhibitory effect on proliferat ion and FSH-induced estradiol production by bovine granulosa cells col lected from small follicles than from large follicles. Thus, it appear s that less differentiated granulosa cells (small follicles) are more sensitive to IL-6 than are highly differentiated granulosa cells (larg e follicles).