Effect of anordrin on the rat anterior pituitary responsiveness to GnRH in vitro

The responsiveness of pituitary explant to pulsatile GnRH(in 199 meduim)and the effect of Anordrin on it were determined by RIA of the basal and promotedsecretion of LH.Pituitaries were taken from proestrous rats.Pulsatile GnRHregime consisted of a 6-min pre-exposure to the hormone followed by the dissolvent199 medium only for 54 minutes.The procedure was repeated for another 1 hour.The results showed that a 6-min pulsatile GnRH exposure stimulated release ofLH;the net increase amounts to 4.3ng/ml after the first exposure(and)significant-ly to 6.8ng/ml after the second exposure.Thus GnRH is capable of not only sti-mulating pituitary explant to produce LH but also showing some priming effect.Anordrin did not influence basal LH secretion but did partially inhibit GnRH in-duced release of LH from 4.3 to 2.5ng/ml in the first hour and from 6.8 to 4. lng/ml in the second hour(P0.01).