The sequential changes in plasma LH and prorenin suggest that gonadotropins stimulate ovarian prorenin release, which may be involved in the process of ovulation.
Prorenin, the enzymatically inactive biosynthetic precursor of renin, is secreted by the kidneys. However, the ovaries appear to be the source of the cyclical increase in plasma prorenin that occurs in the middle of the menstrual cycle. In this study we examined the temporal relationship between changes in plasma prorenin and LH in normal women to determine whether ovarian prorenin secretion might be stimulated by LH. Blood was collected from nine normal women daily for 7 days in the midcycle period and from six of them every 8 h on 6 of these days. Time zero was taken as the highest plasma LH value. The initial rise in LH (-24 h) preceded the initial rise in prorenin (-8 h) and the LH peak preceded the prorenin peak by 8-16 h. These sequential increases in plasma LH and prorenin occurred in the presence of high plasma estradiol levels. While LH fell in parallel with estradiol, the prorenin peak was more sustained and plasma prorenin remained above baseline at 40 and 48 h, at a time when both estradiol and LH had reached a new basal level. These results suggest that gonadotropins stimulate ovarian prorenin release. The timing of the changes in plasma prorenin and its presence in high concentrations in ovarian follicular fluid suggest that prorenin may be involved in the process of ovulation. The results also suggest that changes in plasma prorenin may determine the activity of an ovarian renin system that functions independently of circulating active renin.
Sealey et al. (Wed,) studied this question.