Mitochondrial respiratory efficiency is positively correlated with human sperm motility

OBJECTIVE To correlate sperm mitochondrial respiratory efficiency with variations in sperm motility and with sperm morphologic anomalies. METHODS Sperm mitochondrial respiratory activity was evaluated with a polarographic assay of oxygen consumption carried out in hypotonically-treated sperm cells. A possible relationship among sperm mitochondrial respiratory efficiency, sperm motility, and morphologic anomalies was investigated. RESULTS Mitochondrial respiratory efficiency was positively correlated with sperm motility and negatively correlated with the percentage of immotile spermatozoa. Moreover, midpiece defects impaired mitochondrial functionality. CONCLUSION The results reported in this study support a strong and positive correlation between mitochondrial respiratory efficiency and sperm progressive motility. In addition and in strict agreement with these findings, morphologic alterations of the sperm midpiece, where mitochondria are found, are associated with lower mitochondrial functionality and lower sperm motility. These results confirm the important role played by mitochondria in supplying metabolic energy for sperm motility and provide more insights into the biochemical basis of mitochondria-based asthenozoospermia. On the other hand, the findings reported here open up new and interesting avenues of investigation in the case of semen samples from asthenozoospermic subjects, for which a more detailed investigation can be carried out at the level of single componente of the mitochondrial respiratory chain.