Inhibition of the hamster sperm acrosome reaction by transmethylation inhibitors.

Two inhibitors of somatic cell transmethylation, homocysteine thiolactone (Hcy) and 3--deazadenosine (3--DZA), inhibited the acrosome reactions of hamster sperm in vitro. Hcy (250 microM) or 3--DZA (200 microM) inhibited acrosome reactions by approximately 30% after 4 hours of incubation with washed sperm in a capacitating medium containing epinephrine, taurine, and bovine serum albumin. Inhibition by 3--DZA decreased by 5 hours, but inhibition by Hcy did not. Incubation of sperm with the combination of both inhibitors inhibited acrosome reactions by nearly 60% at 4 hours, and did not appreciably decrease with time up to 5 hours. These results are the first to demonstrate that such inhibitors can interfere with the acrosome reaction and taken together with the effects of Hcy and 3--DZA on somatic cells, suggest that sperm protein and/or phospholipid transmethylation is/are involved in capacitation and/or the acrosome reaction.