A Functional Role for 20<i>α</i>-Hydroxypregn-4-en-3-one in the Rabbit

Abstract

Pituitary luteinizing hormone (LH) stimulates the synthesis and release of 20αhydroxypregn- 4-en-3-one (20α-OH) from rabbit ovarian interstitial tissue. Following coitus, the ovarian output of this progestin remains high throughout most of the preovulatory period and its prolonged secretion can be correlated with high plasma levels of endogenous LH. In the chronically ovariectomized rabbit, primed with estrogen to induce mating, coitus initiates a transient discharge of LH which largely disappears from the circulation within 2 hr. Plasma LH levels in mated ovariectomized rabbits can be maintained, however, by injecting 20α-OH in oil subcutaneously immediately after mating. The results indicate that this progestin acts as a positive feedback agent to prolong and heighten LH discharge in the mated rabbit. (Endocrinology80: 901,1967)