Post-testicular sperm maturation and identification of an epididymal protein in the Japanese quail (Coturnix coturnix japonica).

The role of the avian epididymis in post-testicular development and capacitation was examined to assess whether avian spermatozoa undergo any processes similar to those characteristic of mammalian sperm development. We found no evidence of a need for quail sperm to undergo capacitation and 90% of testicular sperm could bind to a perivitelline membrane and acrosome react. However, computer-assisted sperm analysis showed that 20% of testicular sperm from the quail were capable of movement and only about 12% of the motile sperm would have a curvilinear velocity greater than the mean for sperm from the distal epididymis. Nevertheless, epididymal transit was associated with increases in mean sperm velocity and the proportion of motile sperm. Together, these findings explain why earlier workers have achieved some fertilizations following inseminations of testicular spermatozoa and also demonstrate the need for some epididymal maturation of avian spermatozoa. Analysis of the electrophoretic profile of quail epididymal luminal proteins revealed that only one major protein (∼16 kDa) is secreted by the epididymis and it was virtually the only protein secreted by the ipsilateral epididymis following unilateral orchidectomy. Mass spectrometry showed that this protein is hemoglobin; this finding was confirmed using anti-hemoglobin antibodies. It is suggested that hemoglobin may support sperm metabolism in the quail epididymis, aid in motility, and/or serve as an antioxidant.

[Identification of M(r)22 000 protein in rat epididymal luminal fluid].

OBJECTIVE: To identify the specific protein in the epididymal luminal fluid that may play a role in sperm epididymal maturation or modification on the surface of spermatozoa. METHODS: We compared the differential protein components in the lumen fluids from the caput and cauda segments of the epididymis of normal rats as well as from the cauda segment of experimental left varicocele (ELV) rats by SDS-PAGE or 2D-electrophoresis. The protein spots of interest were selected for MS identification, and the target proteins further characterized by immuno-blot assay. RESULTS: MS analysis showed that one of the most prominent proteins, M(r) 22 000, was identical to the phosphatidylethanolamine-binding protein (PBP), and it was further identified as PBP by immuno-blot assay. CONCLUSION: PBPs were present in a variety of molecular forms in the epididymal luminal fluid, including the glycosylated form, and ELV markedly elevated the PBP level in the cauda luminal fluid of the rats. Thus, the association of this molecule with sperm surface modification remains an interest for future investigation.