Effect of bullfrog LH and FSH on newt testes under different temperatures

Environmental temperature plays important roles for amphibian gonadal function. In this study, we examined the responses of testicular tissue of adult male newts (Cynops pyrrhogaster) to amphibian gonadotropins both in vitro and in vivo under different temperatures. When minced testes were incubated in vitro at different temperatures (8-37 degreesC) under an atmosphere of 95% O-2-5% CO2 for 3 It with bullfrog luteinizing hormone (LH) or follicle-stimulating hormone (FSH), LH stimulated testosterone production more than FSH. The testosterone production increased as the incubation temperature increased. Hypophysectomized newts were injected with bullfrog LH or FSH and maintained at 8 or 18 degreesC. In the 18 degreesC group, the testicular weight of the hypophysectornized control decreased when compared with that of with the intact control. The testicular weight of the LH-treated hypophysectornized group decreased more than that of the hypophysectornized control, indicating that LH induced the evacuation of mature spermatozoa from the testes of LH-treated hypophysectomized newts. In the FSH-treated newts, the testicular weight was greater than that in the hypophysectomized control, and was maintained at a value similar to that of the intact control. In the 8 degreesC group, there was no significant difference in testicular size among the intact control, hypophysectomized control, and FSH-treated newts. LH strongly induced spermiation as it did at 18 degreesC. The plasma testosterone level in the hypophysectornized newts decreased dramatically, but LH was effective in restoring it. Its effect was more potent at 8 degreesC than at 18 degreesC. On the other hand, FSH did not induce a significant increase in the plasma testosterone levels at either temperatures. The results indicate a temperature-dependent difference in responsiveness of the testis both in vitro and in vivo to LH and FSH. (C) 2004 Elsevier Inc. All rights reserved.