Differential contribution of leucocytes and spermatozoa to the generation of reactive oxygen species in the ejaculates of oligozoospermic patients and fertile donors

Abstract

Cells isolated from the ejaculates of a high proportion of patients exhibiting oligozoospermia are characterized by generation rates of reactive oxygen species that considerably exceed those obtained for the normal fertile population. The purpose of this study was to resolve the cellular source of this enhanced activity. Semen samples from a cohort of oligozoospermic patients and a group of fertile controls were fractionated on discontinuous Percoll gradients to generate three cell populations (0, 50 and 100%) of differing density. For each fraction, both the steady-state and the phorbol-ester-induced chemiluminescent signals were significantly (P less than 0.001) greater for the oligozoospermic samples than for the fertile controls. In the fertile donors, leucocytes comprised the major source of reactive oxygen species, particularly in the low-density Percoll fractions; in oligozoospermic patients, however, spermatozoa were identified as a second major source of reactive oxygen species. Particularly striking was an intense phorbol-ester-induced chemiluminescent signal generated by oligozoospermic spermatozoa, purified by passage through isotonic Percoll and free of leucocyte contamination, which was 167 times greater than the median signal generated by the corresponding fraction from the fertile controls (P less than 0.001). These results emphasize the importance of spermatozoa as a major source of reactive oxygen species in oligozoospermia and have implications for the diagnosis and treatment of this condition, as well as for the design of appropriate diagnostic strategies.