Influence of 2-deoxy-D-glucose and energy substrates on guinea-pig sperm capacitation and acrosome reaction

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Abstract
When guinea-pig spermatozoa were suspended in a minimal culture medium (MCM-PL), 2-deoxy-D-glucose (100 .mu.M) and 2-amino-2-deoxy-D-glucose (100 .mu.M) were potent inhibitors of the acrosome reaction without affecting the sperm motility; the N-acetyl derivative 2-acetamido-2-deoxy-D-glucose (2 mM) had no inhibitory effect. The addition of D-glucose (2 mM) partly inhibited the percentage acrosome reaction of spermatozoa suspended in Medium MCM-PL, but DL-.alpha.-glycerophosphate (2 mM) and myo-inositol (2 mM) had no effect. In addition, DL-.alpha.-glycerophosphate (2 mM) did not overcome the inhibitory effect of 2-deoxy-D-glucose on the sperm acrosome reaction. The inhibitory action of 2-deoxy-D-glucose (100 .mu.M) on the sperm acrosome reaction assessed after a 3-h incubation was irreversible and was only completely effective if the sugar was added within 30 min of the start of incubation. When spermatozoa suspended in Medium MCM-PL were treated with 2-deoxy-D-glucose (100-200 .mu.M) for an extended incubation up to 6 h, the inhibitory effect of 2-deoxy-D-glucose was partly overcome. Spermatozoa treated with 2-deoxy-D-glucose had significantly reduced concentrations of ATP after incubation for 2 h in Ca2+ free media, compared with the ATP concentrations of spermatozoa preincubated for 2 h in Ca2+ free media that supported acrosome reactions. The additions of Ca2+ (5 mM) caused a rapid decrease in ATP concentrations of spermatozoa suspended in Medium MCM-PL, while the addition of the monovalent ionophore monensin (50 .mu.M) and Ca2+ stimulated sperm acrosome reactions and an additional decline in the sperm ATP concentrations. Monensin (50 .mu.M) in the absence of Ca2+ caused only a slight decline of the sperm ATP concentrations over the 15-min incubation period. The depletion of the sperm ATP concentrations by 2-deoxy-D-glucose may retard completion of the capacitation process and the resultant acrosome reaction.