Variation of docosahexaenoic acid content in subsets of human spermatozoa at different stages of maturation: Implications for sperm lipoperoxidative damage

The oxidation of phospholipid-bound docosahexaenoic acid (DHA) has been sho wn to be one of the major factors that limit the motile life span of sperm in vitro. Sperm samples show high cell-to-cell variability in life span and , consequently, in susceptibility toward lipid peroxidation. Therefore, we postulated that there is also cell-to-cell variability in DHA concentration in human spermatozoa. In this study, the concentration of DHA in subsets o f human spermatozoa isolated by a discontinuous Percoll density gradient wa s determined by gas chromatography. Four subsets of human spermatozoa were isolated using a discontinuous Percoll gradient: fraction 1 was enriched in immature germ cells and immature sperm, fractions 2 and 3 contained, mostl y, immature sperm with cytoplasmic droplets, and fraction 4 contained, for the most part, morphologically normal sperm, as determined by histochemical analysis. The results indicated that there were significant differences in DHA content in sperm from all 4 fractions. DHA content in sperm from fract ion 1 was 2.5-fold higher than that found in fraction 4. DHA content in mou se sperm obtained from the seminiferous tubules was 3-fold higher than that found in mouse sperm obtained from the epididymis, consistent with the fin dings observed in ejaculated human sperm. The results of this study indicat e (i) there is cell-to-cell variability in the concentration of DHA in huma n sperm and (ii) that there is a net decrease in DHA content in sperm durin g the process of sperm maturation. Mol. Reprod. Dev. 55:326-334, 2000. (C) 2000 Wiley-Liss, Inc.