Interleukin-2 affects steroidogenesis and numbers of bovine ovarian granulosa cells but not thecal cells in vitro

The effect of recombinant bovine interleukin-2 (IL-2) on steroidogenesis and numbers of bovine ovarian granulosa and thecal cells has been studied. Granulosa cells have been examined from both small (surface diameter less than or equal to 5 mm) and large (greater than or equal to 8 mm) follicles, whereas thecal cells from only large follicles were utilized. Estradiol and progesterone production per cell by granulosa cells from large follicles was 2- to 3-times greater than those from small follicles. Increasing doses of IL-2 significantly attenuated FSH-induced estradiol production by cells from small follicles but not large follicles. In general, progesterone production per cell by granulosa cells was almost double that of thecal cells. Moreover, IL-2 significantly attenuated FSH-induced progesterone production by granulosa cells from small and large follicles but had no effect on LH-induced progesterone or androstenedione production by thecal cells. Co-treatment of TNF alpha with IL-2 enhanced the responsiveness of granulosa cells to IL-2. The effect of IL-2 on the numbers of granulosa and thecal cells were studied independently under serum-free conditions and media enriched with 10% fetal calf serum. In serum-free medium containing insulin, IL-2 dosage significantly increased numbers of granulosa cells from large follicles, whereas IL-2 had no effect on numbers of granulosa cells from small follicles or thecal cells from large follicles. When cells were grown in medium enriched with serum, increasing doses of IL-2 significantly inhibited numbers without affecting viability of granulosa cells from small follicles, but had no effect on numbers of thecal cells. Thus, it appears that granulosa cells are more sensitive to IL-2 than are thecal cells.