Addition of an androgen-free epididymal protein extract increases the ability of immature hamster spermatozoa to fertilize in vivo and in vitro

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Abstract
The fertility of spermatozoa from the different epididymal segments of hamsters was tested by in-vivo insemination. Caput and proximal corpus spermatozoa were non-fertile; spermatozoa from the distal corpus epidymidis fertilized 13% (38/290) oocytes and those from the proximal and distal cauda epidymidis 71 and 87%, respectively. When tested by in-vitro insemination, distal corpus spermatozoa penetrated 44% of oocytes while those from the distal cauda fertilized 87% of oocytes. Spermatozoa from the distal corpus recovered in Medium BMOC fertilized 13% (28/219) of occytes in vivo, while those mixed with an epididymal protein preparation (0.8 mg protein/ml) fertilized 24% (49/204; P < 0.01) of oocytes. When dital corpus spermatozoa were inseminated in vivo with 0.8 mg epididymal protein preparation 34% (31/90) occytes were fertilized and only 22% (23/103; P < 0.05) oocytes were fertilized when the proteins were obtained from epididymides of animals castrated for 30 days. When distal corpus spermatozoa were preincubated for 5 h in medium without (control) or with protein preparation (0.8 or 1.6 mg protein/ml), a significant increase in in-vitro oocyte penetration was found (25 compared with 45%; P < 0.05) when the protein was present at 1.6 mg/ml. Androgen-dependent glycoproteins secreted by the epididymis may have a role in the acquisition of fertilizing ability that occurs during sperm maturation.