EFFECT OF ACTIVE AND PASSIVE-IMMUNIZATION WITH LUTEINIZING HORMONE-RELEASING HORMONE ON SERUM LUTEINIZING-HORMONE AND FOLLICLE-STIMULATING-HORMONE LEVELS AND ULTRASTRUCTURE OF PITUITARY GONADOTROPHS IN CASTRATED MALE RATS

The effect of active and passive immunization with luteinizing hormone-releasing hormone (LHRH) on serum LH and follicle-stimulating hormone (FSH) levels and the ultrastructure of the pituitary gonadotrophs was investigated in castrated male rats. Two wk after castration, the animals were immunized with Glu1-LHRH conjugated with human serum albumin (hSA), immunized with hSA only, or left uninjected. Immunogens were administered every 2 wk. Four wk after the initiation of immunization with hSA-Glu1-LHRH, 2 out of 4 rats showed parallel decreases in serum LH and FSH levels associated with a rise of serum antibody titer to LHRH. Serum LH and FSH levels remained suppressed throughout the experiment in these rats. Both LH and FSH levels in hSA-immunized rats or non-immunized rats remained elevated, and typical castration cells containing large vacuoles were found in the pituitary. Although castration cells existed in the pituitary of rats which produced antibody LHRH by active immunization, these cells were markedly degranulated, and secretory granules were scarce in the cytoplasm. In another experiment, rats were injected i.v. with 1 ml sheep anti-LHRH .gamma.-globulin (anti-LHRH) or normal sheep .gamma.-globulin (NSG) every 2 days for 3 wk, starting 1 day after castration, when serum LH and FSH levels were already elevated. All animals which received anti-LHRH showed a decrease in both serum LH and FSH levels, which remained low throughout the study, in a range comparable to those in intact normal male rats. In the animals which received NSG, both LH and FSH levels remained high or increased further throughout the experiment, and the pituitary contained numerous castration cells. Castration cells were completely absent from the pituitaries of rats treated with anti-LHRH, suggesting that castration cells are formed as a result of increased secretion of LHRH. Some FSH gonadotrophs in these castrated rats were atrophic. It was difficult to distinguish the LH gonadotrophs in rats which were either actively or passively immunized with LHRH; however, they seem not to have contributed significantly to the development of castration cells. Antibody to the LHRH decapeptide drastically affected both LH and FSH cells, providing additional evidence for the concept that LHRH represents the physiological LHRH and FSHRH [FSH-releasing hormone].