Rat Ovarian Renin: Characterization and Changes during the Estrous Cycle*

Abstract

To demonstrate the existence and help clarify the function of renin in the rat ovary, we have characterized rat ovarian renin and examined ovarian renin levels during different stages of the rat estrous cycle. We show that high concentrations of active renin are present in the rat ovary (2.9 ng angiotensin I/h/mg). Ovarian renin activity has a pH optimum of about 7.0 and is due to a glycosylated aspartyl protease with an apparent mol wt of 39,000. These properties of rat ovarian renin are identical to previously characterized rat kidney renin. In PMSG-treated immature and adult 5-day cycling rats, ovarian renin was increased about 2-fold at estrus. At all stages of the estrous cycle in the 5-day cycling rat, the ratio of active to inactive ovarian renin was about 3:1, whereas about 90% of the renin in plasma was inactive. In the hypophysectomized diethylstilbestrol-treated rat ovary, over 90% of active renin remained in the residual ovary after the granulosa cells had been expressed, suggesting a theca-interstitial localization for renin. These studies indicate that active renin exists in the rat ovary, that its levels are cyclically increased at estrus, and that this increase may be due to enhanced local production and activation of the renin precursor. These findings greatly strengthen the concept of a functional renin-angiotensin system in the rat ovary.

Ser84 of Human Renin Contributes to the Biphasic pH Dependence of the Renin-Angiotensinogen Reaction

“…3) On the other hand, renin ordinarily has a neutral optimum pH (pH 6.0-8.0), and does not show a typical bell shape in pH dependence against homologous and heterologous angiotensinogens. [4][5][6][7][8][9] The reason for this unique pH dependence has not been elucidated, although Tyr83, 10) Ser84, 11) and Ala317 12) of human renin and His9 11) of a synthetic substrate have been reported to contribute to the pH dependence of the renin-angiotensinogen reaction. The catalytic mechanism of renin is generally thought to be analogous to that of a typical aspartic proteinase, but this cannot explain the neutral optimum pH and the unique pH profile of the renin reaction.…”

Bi-directional actions of estrogen on the renin-angiotensin system

“…Estrogen causes over-expression of the RAS by augmenting both tissue and circulating levels of Aogen (51,52) and renin (53)(54)(55)(56). Plasma renin activity (PRA) increases after estrogen treatment in nephrectomized rats (53).…”

A Case of Renin Producing Leiomyosarcoma Originating in the Lung.

“…It has been reported that 75 percent of the total renin activity is active renin in the rat ovary [38], suggesting that there is a tissue specificity in the processing rate from prorenin to renin. In summary, this is the first case report of renin producing leiomyosarcoma derived from the lung, and is characterized by relatively lower plasma prorenin concentrations.…”