[Illustration: Effect of glycerol and glycerol-plus-catalase additions on sperm motility during incubation at 37° C. (Fig. 10)]
With each increase in glycerol level, motility was reduced during the incubation period. This is shown in Figure 10 along with the effect on motility of adding catalase, which is discussed in the next section.
=Effect of glycerol-plus-catalase on oxygen uptake of diluted semen.= Certain bacteria have been shown to break glycerol down, forming hydrogen peroxide as follows:
Glycerol + oxygen --> lactic acid + hydrogen peroxide.
Hydrogen peroxide is known to be detrimental to sperm. The addition of glycerol to diluted semen first increased oxygen uptake and then reduced it. Since a reduction in sperm survival followed, some harmful action must have taken place with the addition of glycerol at 37° C. To test whether this action could be due to the release of hydrogen peroxide as occurs in certain bacteria, glycerol with catalase--the enzyme which breaks down hydrogen peroxide--was added to a portion of 8 diluted semen samples and the oxygen uptake was recorded. Comparison of the resulting oxygen uptake with glycerol and with glycerol plus catalase is shown in Figure 11.
[Illustration: Effect of additions of glycerol-plus-catalase on oxygen consumption of sperm at 37° C. (Fig. 11)]
Oxygen consumption was increased by the presence of added catalase at all glycerol levels and in the control. Sperm survival during the 3-hour period at 37° C. also was improved by the presence of catalase (Fig. 10). However, the general trend in oxygen consumption produced by the addition of glycerol was not changed greatly. The higher levels of glycerol still stimulated oxygen uptake during the first 20-minute period after the additions and then slowed the rate of oxygen utilization. The rate of utilization was generally higher during the test period in the presence of catalase than without added catalase. It appeared that a part of the harmful effect of glycerol might be due to the formation of hydrogen peroxide. Still, the detrimental effects of the higher levels of glycerol were not completely removed.
Table 16.--Effect of Freezing Procedures on Oxygen Utilization of Bull Sperm in Yolk-Citrate Extender