Oxygen uptake by mitochondria in demembranated human spermatozoa: a reliable tool for the evaluation of sperm respiratory efficiency

In this work we report a relatively simple and fast method for analyzing oxygen consumption and therefore mitochondrial functionality, in individual human ejaculates. This oxygraphic method requires a low number of cells, is highly reproducible and linearly correlates with sperm concentration. Our results showed that oxygen uptake by mitochondria of demembranated sperm cells is significantly stimulated by respiratory substrates and ADP. The RCR values indicate a good coupling between respiration and phosphorylation by sperm mitochondria and thus a well preserved integrity of the mitochondria themselves. Interestingly, whereas the rates of oxygen uptake (V3 and V4), as expected, changed with different sperm concentrations, the RCR values remained constant thus demonstrating a linear response of the assay. The results obtained with the use of a panel of specific inhibitors of the respiratory chain suggested that this method, besides its potential clinical application, can also be useful for a deeper understanding of the biochemical properties of sperm mitochondria and their role in ATP production in human spermatozoa.