The ovarian renin-angiotensin system: Renin-like activity and angiotensin II/III immunoreactivity in gonadotropin-stimulated and unstimulated human follicular fluid

Renin-like activity and angiotensin II/III immunoreactivity in follicular fluids from 34 women stimulated with human menopausal gonadotropin and human chorionic gonadotropin (56.8 ± 6.5 ng angiotensin I per milliliter per hour and 187 ± 21 pg/ml [mean ± SEM], respectively) were much higher (p < 0.001) than in follicular fluids from 12 unstimulated preovulatory women (1.41 ± 0.37 ng angiotensin I per milliliter per hour and 58.5 ± 13.7 pg/ml) and in simultaneously drawn plasma (4.47 ± 0.73 ng angiotensin I per milliliter per hour and 31.8 ± 11.6 pg/ml, respectively; p < 0.001). Plasma renin-like activity and angiotensin II/III immunoreactivity in stimulated cycles did not differ from unstimulated cycles. Follicular fluid angiotensin II/III immunoreactivity correlated significantly with follicular fluid renin-like activity in stimulated (r = 0.72; p < 0.01) and in unstimulated samples (r = 0.86; p < 0.01). Significant correlation was found also between follicular fluid renin-like activity and estradiol. A sharp preovulatory rise of renin-like activity and angiotensin II/III immunoreactivity was noted in unstimulated follicular fluid samples collected on cycle days 13 and 14 compared to days 9 through 12 (p < 0.01). The findings that follicular fluid renin-like activity and angiotensin II/III immunoreactivity are correlated, and that gonadotropins have a stimulatory effect on follicular fluid concentrations support our concept of a physiologic intrinsic ovarian renin-angiotensin system.