Oxygen transport in isolated cardiac myocytes.

A preparation of isolated cardiac myocytes, retaining functional and structural properties of myocytes in the intact heart, has been used to measure intracellular oxygen pressure gradients. These are shallow and do not exceed 2 torr. Oxygen does not limit mitochondrial function in the cardiac myocyte until intracellular myoglobin is almost entirely deoxygenated. Most of the large oxygen pressure gradient in the working heart must be extracellular.