Restoration of seminiferous tubular function after discontinuation of long-term gonadotropin-releasing hormone agonist administration in premature male rats.

We examined whether seminiferous tubular function develops normally after discontinuation of long-term gonadal suppression in premature male rats. Wistar male rats 4 weeks old were subjected to the injection of gonadotropin-releasing hormone (Gn-RH) agonist or normal saline solution as control for 12 weeks. The rats were sacrificed 0 and 6 weeks after discontinuation of the treatment. Histological examinations of the seminiferous tubules immediately after cessation of the Gn-RH agonist treatment demonstrated a stage-related change in specific germ cells. Seminiferous tubules of Gn-RH agonist-treated rats were narrow and irregular in shape, and contained significantly fewer spermatids and pachytene spermatocytes at stages VII to XIV than those in controls. A complete development of spermatogenesis was histologically observed 6 weeks after cessation of the treatment. Leydig cells became atrophic without any reduction in cell number immediately after the treatment, but Leydig cells grew rapidly and were similar in appearance to those in control rats 6 weeks after cessation of the treatment. Serum testosterone concentrations were noticeably suppressed immediately after cessation of the treatment (P < 0.01 vs. control) and reached a similar level to those of controls 6 weeks after the cessation. Testes weights were significantly lower in Gn-RH agonist-treated rats than in control rats and had not fully developed 6 weeks after cessation of the treatment (P < 0.01 vs. control). These results suggest that the testicular function develops normally after cessation of the long-term gonadal suppression in premature rats, although the increase in testicular weight may be slightly influenced.