Effects of lipid peroxidation on chromatin in rabbit and mouse spermatozoa: a cytochemical approach

To extend present knowledge on the possible interactions between lipid peroxidation and chromatin, we studied rabbit and mouse spermatozoa during spontaneous lipid peroxidation. Epididymal spermatozoa were aerobically incubated in high sodium or high potassium media to obtain spontaneous lipid peroxidation in the absence of added promoters. Quantitative cytochemical assays were performed in situ, in individual spermatozoa processed by Feulgen reaction and Gallocyanin-chrome alum (GCA) staining. Our findings show that in both species examined, the spermatozoa chromatin undergoes destabilization associated with marked alterations of the physico-chemical state of the DNA-protein complex. The decrease of Feulgen and GCA-positive material may be explained by DNA damage and implies the release from the nucleus of DNA fragments. Moreover, our data support the idea that during spontaneous lipid peroxidation, the spermatozoa chromatin undergoes destabilization sometimes correlated with increased acid lability of the DNA-protein complex. There are differences in the two species, probably correlated with differences in major protective enzymatic systems against cell damage by autoxidation and, especially, against different kinds of oxygen radicals responsible for initiation of lipid peroxidation.