Carbon Dioxide in Anaerobic Spermatozoan Metabolism

Abstract

The mechanism of CO2 effects in mammalian spermatozoan metabolism is little understood. The demonstration of a need for CO2 in anaerobic metabolism of epididymal-like bovine spermatozoa presented an opportunity for further study of CO2 effects on glycolysis. A PCO2 of 2 to 3% was optimum for maximum glycolysis, while levels above and below this narrow optimum range progressively depressed glycolysis. An initial PCO2 of 1% or greater maintained spermatozoan motility, but lower levels did not. Sperm cells deprived of CO2 for 2 hr or longer did not recover metabolism or motility when regassed with 5% CO2 95% N2, whereas cells first subjected to 5% CO2 demonstrated inhibited metabolism resulting from the removal of CO2 only after the first hour. With fructose as substrate, a study of the addition of several substances revealed that only the complex material egg yolk replaced CO2 in initiating glycolysis. Carbon dioxide was necessary for the anaerobic cellular conversion of pyruvate to lactate. The addition of NADH caused an early, marked uptake of CO2, which could be completely inhibited by γ-(3,4-urelenecyclohexyl) butyric acid, a biotin antagonist.