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R. J. Aitken and J. S. Clarkson

Summary. Addition of the divalent cation ionophore, A23187, to washed populations of human spermatozoa resulted in a sudden burst of production of reactive oxygen species which peaked within 3–5 min. This activity was dependent upon the presence of calcium in the external medium and was unaffected by the mitochondrial inhibitors, oligomycin, antimycin and rotenone. Studies with scavengers of reactive oxygen species revealed that, while reagents directed against singlet oxygen and the hydroxyl radical were without effect, cytochrome C reduced the response to A23187 by about 50%, suggesting that the superoxide anion radical is a major product of the activated human spermatozoon.

The clinical implications of these studies stem from the considerable variation observed between individuals in the levels of reactive oxygen species produced by the spermatozoa. This variability was shown to be inversely related to the ability of the spermatozoa to exhibit sperm–oocyte fusion on exposure to A23187; defective samples exhibited a basal level of reactive oxygen species production which was 40 times that observed with normal functional cells.