[Possible involvement of the renin-angiotensin system in reproduction. II. Occurrence and role in the female reproductive tract].

Biochemical and immunological studies of the last years reveal the existence of an "ovarian renin-angiotensin system (RAS)". Despite of the low angiotensin-conterting enzyme (ACE) activity in the ovary the follicular fluid is rich in angiotensin II (AII). The detection of AII receptors on cells within maturating follicles proves them as AII targets. Therefore, it is supposed that AII may be involved in the regulation of fundamental processes of follicle maturation and/or corpus luteum formation. Further interesting findings are the high concentration of prorenin in the follicle fluid of women causing an increase of the prorenin blood plasma level at time of ovulation, and a second increase of the blood prorenin concentration in the middle of the luteal phase. With respect to the ACE activity in the ejaculate it is imaginable that the smooth muscle tonus of the uterus and the oviduct could be affected by local generation von AII and/or degradation of bradykinin and thus the transit of the semen may be facilitated. Further systematic research is necessary to bring more light into the physiological context and to replace hypothetical interpretations of the findings by exact knowledge.