Abstract
The present study was performed to clarify the synthesis of nitric oxide (NO) and its effect on the expression of transcription factor genes (c-fos, c-jun and ATF-4) during the differentiation of granulosa cells. Granulosa cells prepared from porcine ovarian follicles (1-4 mm diameter) were matured with FSH for 48 h. From 40 h to 48 h of ovine FSH stimulation, nitrite and nitrate increased by 2 folds, and this was accompanied by an increase of cyclic GMP. The cells were exposed to either NO scavenger (carboxy-PTIO: 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxy-3-oxide) or NO donor (NOC18: 2, 2'-(hydroxynitrosohydrazino)bis-ethanamine) before or after NO generation, and further stimulated with ovine LH until 48 h. Removal of endogenous NO (NO scavenger) induced a serious impairment in the LH-induced synthesis of progesterone, whereas NO donor had no significant effect on the synthesis. In the semi-quantitative reverse transcriptase-PCR of the transcription factor mRNAs, removal of endogenous NO resulted in a reduction of c-fos expression, an increase of c-jun and no changes in ATF-4 expression. In contrast, NO donor had no significant effects on the expression of these transcription factor genes. Consequently, the transient generation of NO may have critical roles in the LH-induced expression of transcription factor genes and thereafter transformation of the granulosa cell to the luteal cell.
