THE OVARIAN RENIN-ANGIOTENSIN SYSTEM IN REPRODUCTIVE PHYSIOLOGY

The identification of the presence of prorenin, renin, angiotensinogen , angiotensin-converting enzyme, angiotensin II (Ang II), and Ang II r eceptors in the ovary suggests that there is a functional ovarian reni n-angiotensin system (RAS). It could play a significant role in such a reas of ovarian physiology as follicular development, steroidogenesis, oocyte maturation, ovulation, and follicle atresia. Expression of the ovarian RAS is regulated by gonadotropins. Ang II, a bioactive octape ptide of RAS, has important effects as a paracrine/autocrine regulator at different stages of the reproductive cycle. Ang II modulates ovari an steroidogenesis and formation of the corpus luteum and also stimula tes oocyte maturation and ovulation via Ang II receptors on granulosa cells. In addition, increasing evidence demonstrates that Ang II is a major factor in regulating the function of atretic follicles. In any p hysiologic system, aberrations result in the development of pathologic states. Disturbances in the ovarian RAS can be the cause or the resul t of such reproductive disorders as polycystic ovary syndrome, ovarian hyperstimulation syndrome, ovarian tumors, and ectopic pregnancy. Dat a support the concept of an active and regulated RAS in ovarian follic les. Species differences observed in the expression of ovarian RAS sug gest varying functional roles among species with respect to ovarian ph ysiology. (C) 1997 Academic Press.