Epididymal proteins mimic the androgenic effect on zona pellucida recognition by immature hamster spermatozoa

Abstract

The increase in zona pellucida binding caused by the exposure of cultured proximal corpus epididymidis to 2 μM-5α-DHT (0.87 and 4.20 spermatozoa/egg for control and 5α-DHT group respectively) was lost when 20 μM-cycloheximide was also added to the medium (0.72 spermatozoa/egg). These results were interpreted as meaning that de-novo protein synthesis was required to obtain the effect of androgens. When a fraction enriched in epididymal glycoproteins (EP2-EP6 (18% total protein in epididymal cytosol and 30% in enriched fraction) and depleted of androgens (<120 pg testosterone + DHT/ml) was added to the cultured epididymal tubules, the zona pellucida-binding ability of the contained spermatozoa increased from 0.55 in controls to 2.73 spermatozoa/egg in the extract-treated group (P<0.02). When the enriched fraction was prepared from epididymides of 30-day castrates, the stimulatory effect was lost (1.04 spermatozoa/egg). We suggest that proteins synthesized in the epididymis are required to obtain the effect of androgens and that the glycoproteins EP2-EP6 may be involved.