Glucose Requirement for Mouse Sperm Capacitation in vitro

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Abstract
Requirements for the 3 energy substrates (glucose, lactate and pyruvate) which are present in Whitten''s medium for fertilization of mouse ova in vitro by epididymal sperm were examined. Capacitation of sperm during a 3 h preincubation period occurred equally well in complete medium and in medium from which lactate and pyruvate was omitted. The proportion of ova fertilized by sperm when lactate was omitted from the medium was not significantly different from that obtained with complete medium. Glucose was apparently the major source of energy for capacitation of epididymal mouse sperm, but the presence of cumulus cells or pyruvate was required to maintain ova viability during the incubation with sperm. Ova viability was not maintained by lactate in the absence of pyruvate. The substitution of fructose for glucose in Whitten''s medium resulted in very low fertilization rates similar to those found when glucose was omitted from the medium. The rate at which CO2 was produced from fructose by sperm during a 3 h incubation period was approximately 1/2 of the rate from glucose, suggesting that failure of fructose to support fertilization probably involved deficiencies in its transport or intracellular metabolism to provide adequate energy for sperm motility and capacitation. Rates of CO2 production from C atoms (numbers 1 and 6) of glucose during incubation with sperm were not significantly different, suggesting that glucose was oxidized primarily by the glycolytic pathway during capacitation of sperm.