Effect of active immunization to luteinizing hormone releasing hormone on serum and pituitary gonadotrophins, testes and accessory sex organs in the male rat.

The effects of active immunization to luteinizing hormone releasing hormone (LH-RH) on serum and pituitary gonadotrophins testes and accessory sex organs in the male rat were studied. 6 rats were immunized with synthetic LH-RH and 6 rats served as controls. 12 weeks postimmunization animals were bled and the presence of antibody was determined by radioimmunoassay. Immunoreactive LH and follicle-stimulating hormone (FSH) in pituitary extracts and in serum were measured by double-antibody radioimmunoassay. The immunized rats showed atrophy of the testes and secondary sex organs and they had antibodies in the circulation 12 weeks postimmunization. Serum LH was not detectable in any of the antibody producers and pituitary LH was 1/3 that of the controls. Pituitary FSH in the LH-RH antibody producers was 1/4 that of controls and serum FSH was barely detectable (100-120 ng/ml compared with 313-545 ng/ml in controls). Serum testosterone in immunized rats was .28 ng/ml compared with 3.29 ng/ml in controls. Histological studies revealed a total arrest of spermatogenesis in the immunized rats. It was concluded that antibodies to LH-RH can inhibit the action of indogenous hormone and that LH-RH is the releasing hormone required for release of LH and FSH in the rat.