Testicular immunosuppressive activity in experimental hypogonadism and cryptorchidism

The levels of protectin activity were studied in scrotal and abdominal testes and in testes of hypophysectomized and hormone-treated rats to determine whether the prolonged survival of transplants in the abdominal testis was associated with higher protectin activity and whether the protectin activity was dependent on testosterone production. The levels of the testicular high-molecular weight immunosuppressive activity per gram of tissue or per protein concentration rose progressively in the abdominal testis until 7 days after the rats had been made unilaterally cryptorchid. No such increase was observed in the contralateral scrotal testis. In hypophysectomized rats the levels of the testicular immunosuppressive activity were higher than in normal controls. Increase in the serum testosterone concentrations in the hypophysectomized rats obtained by daily treatment with human chorionic gonadotrophin or pregnant mare serum gonadotrophin was associated with significantly lower levels of the testicular immunosuppressive activity as compared to untreated hypophysectomized animals. In the normal rats estradiol treatment increased the levels of testicular immunosuppressive activity as serum testosterone concentrations decreased. In gel filtration there were clear peaks of immunosuppressive activity eluting at 25, 32 and 44 min, corresponding to Mr of greater than 400,000, 200,000 and 25,000, respectively. These results suggest that the levels of testicular immunosuppressive activity increase when testosterone production decreases and support the earlier suggestion that transplant survival in the rodent testis is not dependent on the maintenance of normal testosterone levels in the recipient testis.