The effect of incubation periods under 95% oxygen on the stimulated acrosome reaction and motility of human spermatozoa

Human sperm samples were prepared on a 30% Percoll gradient and reactive oxygen species (ROS) production was measured. In samples that generated ROS incubation under 95%O-2:5%CO2 for 30 min decreased the proportion of spermatozoa capable of the stimulated acrosome reaction by 40% in comparison to samples incubated under 95%N-2:5%CO2 (P < 0.001, repeated measures analysis of variance), but the degree of inhibition did not increase after more prolonged incubation periods (up to 6 h). The addition of the antioxidants catalase and superoxide dismutase prevented the inhibitory effect of 95%O-2:5%CO2. Leukocyte removal from samples prior to 95%O-2:5%CO2 incubation preserved the ability of the spermatozoa to acrosome react. Sperm motility parameters were less affected by 95%O-2:5%CO2 but track velocity was 64.1 mu m/s +/- 1.96 after 2 h incubation under 95%N-2:5%CO2 compared with 54.7 mu m/s +/- 1.41 after 2 h incubation under 95%O-2:5%CO2 (P < 0.05, repeated measures analysis of variance). Sperm samples that did not generate detectable ROS were not affected by 95%O-2:5%CO2. The toxic effects of incubation under 95%O-2:5%CO2 on human spermatozoa result from increased endogenous ROS production, mostly from leukocytes. High ROS levels inhibit sperm function, with the stimulated acrosome reaction being more susceptible than motility parameters.