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Carbon Dioxide in Anaerobic Spermatozoan Metabolism

Department of Dairy Science, University of Illinois, Urbana

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% C02 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 -(3,4-urelenecyclohexyl) butyric acid, a biotin antagonist.