Factors Affecting Immobilization of Bovine Spermatozoa with CO2 and Their Subsequent Reactivation

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Abstract
The immobilizing effects of CO2 on bovine spermatozoa, followed by reactivation with several pure and mixed gases, were studied in various suspension media by visual microscopic observation in a Bellco Glass, Inc. micro-cell. The motility of spermatozoa in undiluted semen declined sharply upon CO2 gassing. However, complete immobilization was not observed and a gradual increase in the percentage of motile sperm was noted during continued CO2 gassing. The motility of CO2-inhibited sperm cells was completely restored upon exposure to 02. N2, He, air, or various mixtures of CO2, N2, and O2 containing up to 20% CO2. Complete immobilization was observed in suspensions containing 10 X 106 cells/ml in saline and in the dialyzable fraction of seminal plasma. Immobilization was incomplete in IVT, in IVT containing varying percentages of seminal plasma, and in the nondialyzable fraction of seminal plasma. Recovery of motility upon oxygenation was observed to be optimal where complete immobilization did not occur. The addition of bovine serum albumin to the dialyzable fraction of seminal plasma showed almost the same effect as shown by the nondialyzable fraction. On the other hand, dextran additions did not show any beneficial effects. Results of these investigations suggested that the buffering capacity of the medium, levels of certain electrolytes, and the nondialyzable fraction of the seminal plasma are, at least in part, important factors in maintaining sperm motility under CO2.