In vitro fertilizing capacity of sperm from FSH-treated photoinhibited Djungarian hamsters (Phodopus sungorus)

(Requests for offprints should be addressed to E Nieschlag) In hypogonadal male Djungarian hamsters FSH alone can induce normal spermatogenesis. However, for the induc-tion of mating behavior, supplementation with testoster-one is necessary. We have here investigated, by in vitro fertilization, whether sperm produced by photoinhibited hamsters treated with FSH alone can fertilize without tes-tosterone. Photoinhibited hypogonadal male Djungarian hamsters were injected daily with human FSH (10 IU; Fertinorm) for 5–7 weeks. The hormone stimulated re-growth of the testes. Neither body weight nor the weights of the androgen-dependent organs – epididymides, pros-tates, accessory glands – showed significant diVerences from photoinhibited controls; furthermore FSH treatment did not raise intratesticular or serum testosterone levels. In eleven out of the twelve FSH-treated photoinhibited hamsters, elongated spermatids were found in the testes; in five out of nine epididymides, sperm was found by histological examination. In two out of the twelve FSH-treated hamsters, the amount of sperm in the caudal part of the epididymis was suYcient for in vitro fertilization with oocytes collected from superstimulated females. These spermatozoa fertilized 16–29 % of the oocytes. Spermatozoa from photostimulated controls produced similar levels of fertilization