Hamster Zonae Pellucidae cannot Induce Physiological Acrosome Reactions in Chemically Capacitated Hamster Spermatozoa in the Absence of Albumin1

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Abstract
Cauda epididymal hamster spermatozoa were capacitated with D-penicillamine in a chemically defined (protein-free) medium (= "chemical" capacitation). Hamster zonae pellucidae were incabable of inducing functional acrosome reactions in chemically capacitated hamster sperm in a protein-free medium during sperm-egg coincubation. The culture medium used throughout incubation was a modified Tyrode''s solution containing 10 mM sodium lactate, 100 .mu.M soium pyruvate and 1.0 mg/ml polyvinylalcohol (TLP-PVA). Sperm motiity was maintained in all media with PHE (20 .mu.M penicillamine, 100 .mu.M hypotaurine, and 1.0 .mu.M epinephrine). Additional D-penicillamine (125 or 500 .mu.M) or 3 mg/ml bovine serum albumin (high control: TALP-PVA) was used to capacitate sperm during preincubation at 1-2 .times. 106 sperm/ml for 4.0 h at 37.degree.C in 5% CO2 in air. Sperm were then coincubated (2 .times. 104 sperm/ml) with cumulus-free hamster eggs in TALP-PVA or TLP-PVA .+-. additional D-penicillamine (total: 500 or 125 .mu.M) for 1.5 or 6.0 h. Percent egg penetration was used as the definitive index of spem capacitation and functional acrosome reactions. Chemically capacitated sperm did not penetrate eggs (0.0 .+-. 0.0%) in the absence of albumin during 1.5 h of sperm-egg coincubation. When sperm were chemically capacitated with 125 .mu.M or 500 .mu.M D-penicillamine, then coincubated with eggs for 6.0 h in the absence of albumin, only 18.8 .+-. 28.6% and 23.7 .+-. 29.7%, respectively, of eggs were penetrated. Significantly (p < 0.05) more eggs (67.7 .+-. 22.4%) were penetrated when coincubated with chemically capacitated sperm for 1.5 h in medium containing albumin. These results demonstrate that zonae pellucidae of hamster eggs require the presence of albumin to efficiently induce functional acrosome reactions in sperm that are chemically capacitated with D-penicillamine.