Effect of hypophysectomy, sex of host, and/or number of transplanted testes on Sertoli cell number and testicular size of syngeneic testicular grafts in Fischer rats.
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One or more neonatal testicular grafts were transplanted for 60-65 days into young adult inbred Fischer rats to determine the effect of hypophysectomy, sex of host, and/or the number of transplanted testes on testicular size and Sertoli cell number. All host rats had been castrated or ovariectomized and some were hypophysectomized as well. At the end of the treatment, testes were fixed and embedded in Epon before histologic sections (0.5 micrometer or 20 micrometers) were evaluated by stereology. Testicular grafts placed in castrated adult male rats with intact pituitaries weighed more (p < 0.01) and had more (p < 0.01) Sertoli cells than those placed in hypophysectomized hosts. Testicular grafts that were recovered from hypophysectomized rats 34 days posttransplantation and placed in pituitary-intact males for 30 day had larger (p < 0.05) parenchymal weights and more Sertoli cells than did testes re-transplanted into hypophysectomized rats. However, this delayed period of Sertoli cell proliferation id not extend to 65 days of hypophysectomy. When two or four testes were transplanted into castrated males or ovariectomized female hosts for 65 days, there was no difference in the graft weights or Sertoli cell numbers between sexes. Four transplanted testes per rat produced more (p < 0.01) total testicular parenchyma and a greater (p < 0.01) number of Sertoli cells per testis than did two tests regardless of sex of the host. This model has shown that the period of Sertoli cell proliferation can be delayed by hypophysectomy, that Sertoli cell number can be influenced by endogenous hormones, and that a major component in regulation of testicular size is at the level of the testis in this model. Hence, this model should facilitate study of experimental endocrine manipulation control and potential experimental intervention to increase Sertoli cell number and testicular size.