Isolated rat cardiac myocytes as an experimental tool in the study of anoxic cell injury. Effect of reoxygenation — A preliminary report

Rat cardiac myocytes were isolated by heart perfusion in the presence of collagenase and incubated in the absence or presence of oxygen. As a result of anoxia, there was a gradual increase in plasma membrane permeability, noted as a decrease in trypan blue exclusion frequency, leakage of cytosolic lactate dehydrogenase and intracellular accumulation of the isotope compound ⁹⁹Tc^m-gluconate. The changes in plasma membrane permeability properties were preceded by a marked decrease in cellular ATP level and an increased proportion of contracted myocytes. The ability of the myocytes to resynthesize ATP and to recover from the anoxic injury upon reoxygenation decreased gradually with the length of initial anaerobic incubation during the first 25 min and disappeared after 30 min of anoxia, indicating that the anoxic injury to the isolated rat cardiac myocytes becomes irreversible after 25 – 30 min of anoxia. It is suggested that a decreased energy level is of primary importance for the initiation of cell injury in anoxia and that it is followed by cell contracture and subsequently by a disturbed plasma membrane function, cell swelling and death. This experimental model system of isolated viable rat cardiac myocytes is suitable for problems dealing with reversibility of myocytic injury.