Metabolism of Sea Urchin Spermatozoa and Induced Anaerobic Motility in Solutions of Amino Acids

Abstract

Summary

1. The metabolism of sea urchin spermatozoa has been examined in sea water containing amino acids which, as had been previously shown, greatly extend the functional life span of these cells. 2. The oxygen uptake of spermatozoa in sea water containing amino acid resembles that of spermatozoa in normal sea water in that a high initial rate is followed by a steady decrease. 3. In the presence of amino acid, however, the initial rate is lower than that of the controls, the degree of inhibition increasing as the concentration of the amino acid is increased. 4. The low rates of oxygen uptake attained after a period of senescence are significantly higher in the presence of amino acid than in the controls. 5. Suspensions of spermatozoa in sea water show a secondary rise in O₂ uptake shortly after a period of extremely low, or non-existent, oxygen uptake following loss of motility and fertilizing capacity. 6. This secondary rise is much delayed in the presence of amino acid, corresponding to the extended period of motility and fertilizing capacity. 7. The secondary rise is associated with the growth of bacteria as the spermatozoa die and disintegrate. 8. The addition of penicillin (50 units per ml) is efficacious in checking bacterial growth and the secondary rise in oxygen uptake in suspensions of senescing spermatozoa. 9. In the presence of amino acid, motility and fertilizing capacity can be maintained near their original level for many hours after the rate of oxygen uptake has dropped to less than 5% of the initial rate. 10. Previous evidence that the spermatozoa do not metabolically utilize the added amino acid to any appreciable extent is further supported by the results of experiments with carboxyl C¹⁴-labelled glycine. 11. The total oxygen consumption of spermatozoa in the presence of amino acid exceeds that of the controls, which means that the death of the spermatozoa under ordinary conditions is not due to substrate exhaustion but rather to the inability to utilize fully their endogenous substrate. 12. While sea urchin spermatozoa in sea water are quickly immobilized by lack of oxygen, the presence of amino acids enables them to remain highly active for as long as 6 hours at room temperature. 13. No significant glycolysis, CO₂ production, production of ammonia or urea formation is found to occur anaerobically in the presence or absence of amino acid and glycolyzable sugar.