Effect of steroids in combination with LH-RH on the release of LH and FSH in LH-RH-primed immature male rat.

LH and FSH release of immature male rats was remarkedably enhanced by LH-RH if primed with LH-RH one hour before. The effect of exogenous steroids on the action of the second LH-RH was investigated. C-18, C-19 and C-21 steroids in different doses were tested. Blood samples were collected from the jugular vein immediately before and 30 min after the second LH-RH injection. Serum LH and FSH were determined by respective radioimmunoassays. The concomitant increase of LH and FSH was not induced by all the steroids administered iv. Estrone or 17alpha-hydroxyprogesterone suppressed LH and FSH release. Estradiol-17beta preferentially suppressed LH release. Cortisone, progesterone or dehydroepiandrosterone significantly facilitated FSH release, whiel 20alpha-dihydroprogesterone or 20beta-dihydroprogesterone selectively promoted LH release. The sc injection of most steroids dissolved in oil tended to augment the acute release of LH but not FSH. 20alpha-Dihydroprogesterone was particularly potent in this concern. Dehydroepiandrosterone or androstenedione was effective in maintaining FSH release for a longer period. These data revealed that potentiated LH and FSH release induced by the second LH-RH was readily modified by steroids administered simultaneously.