DIFFERENTIAL MODULATION OF PORCINE THECA, GRANULOSA, AND LUTEAL CELL STEROIDOGENESIS INVITRO BY TUMOR-NECROSIS-FACTOR

The role of tumor necrosis factor alpha (TNFalpha) in ovarian function was investigated using in vitro culture of theca and granulosa cells isolated from gilt follicles (4-6 mm) and small (SLC) and large (LLC) luteal cells from mid-cycle corpora lutea. TNFalpha did not affect bas al accumulation of progesterone (P) by theca cells after 72 h of cultu re. However, TNFalpha (0. 1 - 100 ng/ml) caused a marked dose-dependen t noncytotoxic inhibition (p < 0.05) of LH or LH + insulin (I)-stimula ted P accumulation by theca cells after 72 h. Maximal inhibitions aver aged 87 +/- 6% at 5 ng/ml TNFalpha for LH-stimulated P and 69 +/- 4% a t 50 ng/ml TNFalpha for LH + I-stimulated P. The inhibitory effect of TNFalpha, evident by 24 h after culture, progressively increased on Da ys 2 and 3 of culture. The effect of TNFalpha on theca cells was media ted by cAMP generation as evidenced by TNFalpha inhibition of LH-induc ed cAMP accumulation and P accumulation in response to LH and forskoli n but not dibutyryl cAMP. Consistent with this, TNFalpha had no effect on increased P accumulation by theca cells in the presence of 22-hydr oxycholesterol or pregnenolone alone, but inhibited further increases in P accumulation stimulated by LH plus sterol substrates. Unlike that in theca cells, FSH-induced P accumulation in granulosa cell cultures was slightly enhanced (p < 0.05) by low doses of TNFalpha (0. 1, 0. 5 , and 1.0 ng/ml) after 72 h, while higher doses (5-50 ng/ml) did not a lter P accumulation. Furthermore, in experiments with luteal cells, TN Falpha had no effect on P accumulation in cultures of SLC or LLC after 36 h. The effect of INFalpha on porcine theca cells may indicate a ro le in preventing premature follicular luteinization; together with pre vious evidence, this suggests a complex and possibly evolving physiolo gical role for TNFalpha during follicular development.