2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN ALTERS STEROID SECRETION BUT DOES NOT AFFECT CELL VIABILITY AND THE INCIDENCE OF APOPTOSIS IN PORCINE LUTEINISED GRANULOSA CELLS

The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a by-product of human industrial activity, was found to affect ovarian steroidogenesis in animals, but the mechanism of its action is still unclear. The aims of the study were to examine the effect of TCDD on (1) progesterone (P-4) and oestradiol (E-2) production by granulosa cells isolated from medium (3-6 mm) and preovulatory (>= 8 mm) porcine follicles, (2) the viability of the cells, and (3) the incidence of apoptosis. Porcine granulosa cells were cultured (48 h) with or without TCDD (100 pM, 100 nM). Steroid hormone concentrations in the medium were determined by radioimmunoassay. The viability of granulosa cells was tested spectrophotometrically (alamarBlue (TM) assay). Apoptosis was evaluated by flow cytometry using Annexin V and by TUNEL assay. The higher dose of TCDD (100 nM) significantly inhibited P-4 and stimulated E-2 production by luteinised granulosa cells isolated from medium follicles. The lower dose of TCDD (100 pM) significantly stimulated P-4 and inhibited E-2 secretion by the cells isolated from preovulatory follicles. None of the two TCDD doses affected cell viability or induced apoptosis in granulosa cells. In conclusion, TCDD directly affected steroid production by granulosa cells obtained from mature pigs, but the effect of TCDD was not due to its cytotoxicity.