Distribution of α- and δ-tocopherols in seminal plasma and sperm fractions of men with normal and abnormal semen parameters.

The aim of this study was to investigate the presence of the different isoforms of tocopherol (T) in seminal plasma (P) and in the sperm fractions of individuals with abnormal (group 1) and normal (group 2) sperm parameters; the relationships between these isoforms and conventional sperm parameters were also explored. Two vitamin E homologues, α-T and δ-T, were identified in the semen of all participants. Although α-T and δ-T concentrations were similar in the semen of the 2 groups, group 1 showed a lower α-T ratio (S/P) (0.90 vs. 1.20, P < .001) and δ-T ratio (0.86 vs 1.13, P = .007) than group 2. In addition, both T ratios were correlated with the percentage of viable cells, detected by eosin staining. These results suggested that α-T and δ-T are not homogeneously distributed in the semen fractions; in normal semen they are more concentrated in the sperm membrane, whereas in abnormal semen the damaged sperm cells may release both Ts in the plasma. To verify whether sperm membrane breakage could alter α-T and δ-T distribution between the seminal plasma and the spermatozoa, normal sperm samples were sonicated; after sonication a consistent sperm plasma membrane fragmentation, highlighted by transmission electron microscopy, and a concomitant release of α-T and δ-T were observed. In conclusion, the Ts coupled directly with the sperm membrane seem to play the main protective role in the semen, and the release of α-T and δ-T in the P fraction is probably an index of lower antioxidant power and sperm quality.