A comparison of baseline and induced DNA damage in human spermatozoa from fertile and infertile men, using a modified comet assay

Baseline DNA damage in spermatozoa from fertile and infertile men was compared using a modified alkali single cell gel electrophoresis (comet) assay. Semen from normozoospermic fertile, normozoospermic infertile and asthenozoospermic infertile (World Health Organization criteria, 1992) samples were studied. No significant difference was observed in levels of baseline damage between the three groups. A median value for baseline damage of approximately 20% (80% head DNA) was obtained in all samples. Irradiation with X-rays (5-30 Gy) produced no additional damage in fertile samples when median values were examined. However, irradiation with 30 Gy X-rays produced significant damage in both infertile groups. Hydrogen peroxide (40 microM) treatment induced significant damage in the asthenozoospermic group, whereas 100 microM H2O2 was required to cause significant damage in the normozoospermic fertile and infertile samples. Within the fertile population a subgroup in which percentage head DNA was greater than 80% was observed in both treated and untreated specimens. This subgroup significantly decreased with treatment in both infertile groups. We conclude that the asthenozoospermic infertile group is more susceptible to damage than the normozoospermic infertile group, which in turn is more susceptible than the fertile group. The fertile group contains a resistant subpopulation of spermatozoa with relatively intact DNA.