The relative contributions of fructose, lactate, acetate, citrate and inositol to the aerobic metabolism of ram spermatozoa have been examined in various combinations of these substrates. By using isotopically labelled compounds it was shown that fructose and lactate were important substrates oxidized by ram spermatozoa incubated in diluents containing fructose and low levels of other metabolites. Although the addition of sodium lactate to a spermatozoal suspension caused no change in the amount of fructose converted to lactate, there was a reduction in the amount of fructose oxidized to carbon dioxide.
At the levels of acetate and citrate occurring in semen, their effect on the oxidation of fructose by ram spermatozoa was small. Higher concentrations of these compounds, however, caused a decrease in fructose oxidation. The addition of citrate and acetate to a fructosecontaining diluent did not affect the amount of fructose utilized by ram spermatozoa. While acetate had no effect on the accumulation of lactate from fructose, the presence of the high levels of citrate decreased the amount of lactate produced.
Thus fructose and lactate are the main metabolites for unwashed ram semen incubated under aerobic conditions in a diluent containing fructose. In these circumstances, a quantitative measure of the oxidation of these substrates, coupled with an estimation of fructolysis, should give a good measure of the metabolism of the cell.
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