Effect of serum sex steroids on pituitary LH response to LHRH and LH synthesis.

To determine the factors responsible for the sex difference in luteinizing hormone (LH) response to luteinizing hormone-releasing hormone (LHRH) observed earlier in pituitary cultures, we examined the effects of serum, 17 beta-estradiol, and testosterone on pituitary LHRH-responsiveness and LH synthesis. Cultures prepared from female rats were maintained in medium supplemented with serums. Dextran-coated charcoal (DCC) adsorption of female rat serum reduced, whereas DCC adsorption of male rat serum increased the pituitary LHRH-responsiveness, indicating the existence of stimulatory factor(s) in female rat serum and inhibitory factor(s) in male rat serum. Readdition of testosterone to DCC female rat serum significantly reduced LH release in response to LHRH (78-32% of the control) without affecting total LH content. Readdition of 17 beta-estradiol to DCC female rat serum significantly increased the LH release in response to LHRH, cellular LH content, and 3H-labeled precursor uptake and incorporation into immunoprecipitable LH. These results indicate that the sex difference in LHRH responsiveness may be attributed to the stimulatory effect of 17 beta-estradiol and the inhibitory effect of testosterone on the LH cells.