Regulation of the epididymal synthesis of P26h, a hamster sperm protein.

We have previously identified a 26-kDa epididymal hamster sperm glycoprotein (P26h) that is involved in gamete interaction. This protein is added to the acrosomal cap during epididymal transit of spermatozoa. Because the epididymis secretes proteins under androgen control, the aim of this study was to document the testicular control of the epididymal ontogenesis of P26h. The cytosolic fraction of the epididymides of male hamsters of different ages, prepared by ultracentrifugation, was used as well as those from mature males at different times following castration. These extracts were Western blotted and probed with an anti-P26h antiserum. P26h was initially immunodetectable in extracts prepared from hamsters 4 weeks of age, and the signal increased up to the 7th week of age. The P26h signal decreased rapidly after castration until the antigen was undetectable at 3 days following castration. Administration of testosterone to 3-week-old male hamsters resulted in the epididymal expression of P26h earlier than that observed in untreated or control animals. These results suggest that P26h protein expression in hamster epididymis is under testicular androgen control.