Glucose Requirement for Mouse Sperm Capacitation in vitro

Abstract

The requirements for glucose lactate and pyruvate which are present in Whittens medium for fertilization of mouse ova in vitro by epididymal sperm were examined to determine to what extent fertilization occurred when complete medium was used when all energy sources were omitted and when the only energy source was glucose (5.55 mM) or fructose (5.5 mM). The possibility that pyruvate was also requir ed for sperm capacitation was determined by examining the effect of preincubating the sperm in media with and without pyruvate upon their subsequent ability to fertilized ova. A possible effect of sodium lactate on sperm capacitation was examined by removing ova at various times after mixing with sperm to observe any differences in the proportion of ova fertilized in Whittens medium with or without sodium lactate and with pyruvate and glucose. Capacitation of sperm during a 3-hour preincubation period occurred equally well in complete medium and in medium from which lactate and pyruvate ahd been omitted. Glucose is thus the major source of energy for capacitation of epidiymal mouse sperm but the presence of cumulus cells or pyruvate is required to maintain ova viability during the incubation with sperm. The substitution of fructose for glucose in Whittens medium resulted in very low fertilization rates similar to those found when glucose was omitted from the medium. Measured rates of carbon dioxide production in this situation indicates the possibility that the failure of fructose to support fertilization probably involves deficiencies in its transport or intracellular metabolism to provide adequate energy for sperm motility and capacitation.