The oxygen dependence of mitochondrial oxidative phosphorylation and its role in regulation of coronary blood flow.

The oxygen dependence of mitochondrial oxidative phosphorylation measured in isolated cells of cardiac and non-cardiac origin are affected by the metabolic state of the cells. The contribution of oxygen diffusion to the measured P50 value in resting cells is small. In cardiac myocytes, and possibly in the other cells as well, this contribution may become significant near maximal levels of respiration. The influence of cellular energy metabolism on the oxygen dependence of respiration in cardiac myocytes suggests strongly that mitochondrial oxidative phosphorylation in these cells is an oxygen sensor for adjusting coronary vascular tone during normal cardiac function.