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Free thiols in human spermatozoa: correlation with sperm DNA integrity
1Division of Urology, Department of Surgery, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.
Objectives:
To examine the levels of sperm protamine free sulfhydryl or thiol (SH) groups and DNA denaturation (DD) in semen from fertile and infertile men.Methods. Semen samples were obtained from consecutive nonazoospermic men presenting for infertility evaluation (n = 66) and fertile men presenting for vasectomy (n = 10). The standard semen parameters (sperm concentration, motility, and morphology), sperm DD, and SH content were monitored. Sperm DNA integrity was evaluated by flow cytometry analysis of acridine orange-treated spermatozoa and expressed as the percentage of spermatozoa demonstrating denatured DNA.
Results:
The mean (+/- SE) levels of sperm SH groups and the percentage of spermatozoa with DD were significantly higher in the infertile men than in the fertile men (SH groups 1083 +/- 97 and 570 +/- 101 nmol/10(6) spermatozoa, respectively; and DD 21% +/- 1.7% and 8.9% +/- 1.9%, respectively). The levels of sperm SH groups and DD correlated positively (r = 0.53). Also, the levels of sperm SH groups and DD correlated negatively with the standard semen parameters.
Conclusions:
Our data demonstrate that sperm SH content correlates positively with sperm DD and that significantly higher levels of sperm DD and SH content are found in infertile men than are found in fertile men. These data suggest that the enhanced susceptibility of sperm DNA to denaturation in infertile compared with fertile men may be associated with incomplete oxidation of the sperm SH groups.