Ovary and ovulation: Nitric oxide concentrations in the follicular fluid and apoptosis of granulosa cells in human follicles

To study the relationship between follicular atresia, apoptosis, and nitric oxide (NO) generation in follicular development, steroidogenesis, NO levels in follicular fluid and apoptosis were analysed in the various sized follicles of women receiving ovarian stimulation with human menopausal gonadotrophin (HMG)-human chorionic gonadotrophin (HCG) treatments for in-vitro fertilization (IVF)-embryo transfer. The follicles were divided into three groups by diameter: large follicle, > or = 18 mm; medium follicle, > or = 12 and < or = 15 mm; small follicle, < or = 10 mm. Follicular fluid was obtained from 20 women 34 h after HCG administration, and the concentrations of oestradiol, progesterone and testosterone, and nitrite, nitrate, arginine and citrulline were measured. Granulosa cells obtained from each group of follicular fluid were stained with Hoechst dye, and nuclear morphology was examined by a fluorescence microscopy. Oestradiol and progesterone concentrations in large follicles were significantly (P < 0.01) higher than those in medium or small follicles, and testosterone concentrations in small follicles were significantly (P < 0.01) higher than those in large follicles. There were no significant differences in the concentrations of nitrite, nitrate, arginine and citrulline among three groups. The percentage of apoptotic cells with nuclear fragmentation was significantly (P < 0.01) higher in small follicles than in large follicles. The present results suggested that small follicles with poor response to HMG may undergo atresia through apoptosis. No significant difference in the follicular NO level between large and small follicles led us to speculate on a different responsiveness to NO in these two types of follicles.