Receptors for insulin-like growth factor-I and tumor necrosis factor-alpha are hormonally regulated in bovine granulosa and thecal cells

摘要

Mastitis induces release of tumor necrosis factor-alpha (TNF alpha) and has been linked with reduced reproductive performance. To further elucidate the role and mechanism of action of TNF alpha on ovarian cells, the effect of TNF alpha on insulin-like growth factor-I (IGF-I)-induced steroidogenesis and IGF-I binding sites in granulosa and thecal cells as well as the hormonal regulation of TNF alpha receptors were evaluated. Granulosa and thecal cells were obtained from small (1-5 mm) and large (greater than or equal to8 mm) bovine ovarian follicles, respectively, and cultured for 3-4 days. During the last 2 days of culture, cells were treated with various hormones and steroid production and specific binding of I-125-IGF-I and I-125-TNF alpha was determined, Two-day treatment with 30 ng/ml of TNF alpha decreased (P < 0.05) IGF-I-induced estradiol production by granulosa cells and IGF-I-induced androstene dione production by thecal cells. Two-day treatment with 10 and 30 ng/ml of TNF alpha decreased (P < 0.05) specific binding of I-125-IGF-I to thecal cells, but had no effect on specific binding of I-125-IGF-I to granulosa cells, or on specific binding of I-125-IGF-II to thecal cells. TNF alpha did not compete for I-125-IGF-I binding to granulosa or thecal cells whereas unlabeled IGF-I suppressed I-125-IGF-I binding. Insulin inhibited (P < 0.10) whereas FSH had no effect on the number of specific I-125-TNF alpha binding sites in granulosa cells. In contrast, LH increased (P < 0.10) whereas insulin had no effect on specific I-125-TNF alpha binding sites in thecal cells. These results suggest that IGF-I and TNF alpha receptors in granulosa and thecal cells are regulated by hormones differentially.