Role of tumor necrosis factor in preovulatory follicles of swine

The effects of tumor necrosis factor (TNF) on cultured porcine granulosa ce lls that were obtained from preovulatory follicles were studied with regard to following parameters: 1) TNF receptor type I expression, 2) progesteron e receptor and transforming growth factor beta receptor type II (TOR II) as markers of luteinization, 3) proliferation, and 4) apoptosis. For comparat ive purposes the effects of TNF were also studied on insulin/forskolin-trea ted cells, as this treatment is well established to induce luteinization. C ytochemical methods followed by semiquantitative analysis were used. Our da ta show that TNF treatment upregulates TNF receptor type I expression in gr anulosa cells. TNF downregulates the expression of T betaR II of insulin/fo rskolin-stimulated and of unstimulated cells. The progesterone receptor is also downregulated by the cytokine after insulin/forskolin-induced luteiniz ation. Supplementation of the medium with TNF leads to increased proliferat ion and at the same time it induces apoptosis. Our results indicate that TN F exerts an inhibitory influence on luteinization and that TNF influences t he balance between follicular growth (proliferation) and atresia (apoptosis ).