The objective of the present studies was to determine the effect of cytokines on FSH-induced estrogen production by granulosa cells from small (1-5 mm) and large (> or = 8 mm) bovine follicles. FSH-induced estradiol production by granulosa cells from large follicles (expressed as pg estradiol/10(5) cells/24 hr) was not affected (P > .05) by 10 or 100 ng/ml of interleukin (IL)-1 beta, 10 or 100 ng/ml of tumor necrosis factor-alpha (TNF alpha) or 100 ng/ml of IL-2. In contrast, 100 ng/ml of IL-1 beta, IL-2 or TNF alpha inhibited (P < .05) FSH-induced estradiol production by 31%, 55% or 72%, respectively in cells from small follicles. Interferon-alpha (IFN alpha; 100 U/ml) inhibited (P < .05) FSH-induced estradiol production by 61% and 20% in cultures of cells from small and large follicles, respectively. Interferon-beta (IFN beta; 100 U/ml), interferon gamma (IFN gamma; 100 U/ml) and bovine trophoblast protein-1 (bTP-1; 100 U/ml) inhibited (P < .05) estradiol production by 47%, 71% and 28%, respectively in cells from small follicles, but had no effect (P > .05) on FSH-induced estradiol production in cells from large follicles. TNF alpha binding protein-I blocked (P < .05) the inhibitory effect of TNF alpha on FSH-induced estradiol production by cells from small follicles. Viability of granulosa cells was not affected (P > .05) by the various cytokines. In summary, cytokines have little or no effect on FSH-induced estradiol production by bovine granulosa cells collected from large follicles, whereas cytokines (bTP-1 < or = IL-1 beta < IL-2 = IFN beta < IFN alpha < TNF alpha) have potent inhibitory effects on FSH-induced estradiol production by granulosa cells collected from small follicles. Thus, it appears that less differentiated granulosa cells (small follicles) are more responsive to cytokines than are highly differentiated granulosa cells (large follicles).