Instability of nuclear chromatin in the ejaculated spermatozoa of fertile men

In the present study of 15 fertile men, a mean of 89 +/- 3% of ejaculated cells had nuclei which were stable after treatment with 1% sodium dodecyl sulphate (SDS). Examination of repeated ejaculates demonstrated the constancy of the response of ejaculated spermatozoa from different men to SDS treatment. After 5 cycles of washing, the percentages of cells with stable nuclei after SDS treatment declined from 85 +/- 3 to 46 +/- 6% and ranged from 12 to 66% for different men. The supernatant derived from the first wash inhibited the nuclear chromatin decondensation of washed spermatozoa. Treatment of washed spermatozoa with 1 mM-zinc (which binds to -SH groups) or 1 mM-copper (which promotes oxidation of -SH groups to -S-S-) resulted in a significant increase in the proportion of cells with stable nuclear chromatin. However, the stabilizing effects of zinc could be reversed with continued washing of the cells, whereas the nuclei of copper-treated cells remained stable to SDS after additional washing. We conclude that (1) the number of spermatozoa with nuclei that are insufficiently stabilized by disulphide bonds is much higher in the semen of fertile men than was previously thought, (2) significant differences exist among fertile men in the proportions of ejaculated spermatozoa extensively stabilized by disulphide bonds, and (3) removal of seminal plasma and/or cellular contaminants (zinc) is necessary to unveil the instability of the nuclear chromatin in the ejaculated spermatozoa of fertile men.