Serum LH and FSH following Passive Immunization Against Circulating Testosterone in the Intact Male Rat and in Orchidectomized Rats Bearing Subcutaneous Silastic Implants of Testosterone

Subcutaneous Silastic implants were designed to release quantities of testosterone approximating that produced by the rat testis and appropriate testosterone treatment was found to produce a physiologic inhibition of both LH and FSH secretion in orchidectomized rats. In rats bearing such testosterone implants, intravenous injection of an ovine anti-testosterone serum (0.3 cc) was sufficient to completely abolish the inhibitory effects of the testosterone implant for a period of 3 days as judged by the development of typical post-castration increases in serum LH and FSH. When this dose of antiserum was administered to intact adult male rats, the increases in serum LH on days 1, 2, and 3 post-injection were approximately 19%, 15%, and 11% of those observed in untreated castrates. Increases in serum FSH in antiserum injected rats followed a pattern similar to that for serum LH but the response was slightly greater (19%, 23%, and 22% of the castrate response) and there was no indication of a decreasing effect during the three days following injection. In these experiments, passive immunization against testosterone in intact male rats produced a clearcut stimulation of both LH and FSH release, but produced no data to support the suggestion that the intact testis can secrete nonsteroidal compounds capable of producing a differential inhibition of FSH secretion.