OXYGEN-INDUCED ENZYME-RELEASE - EARLY EVENTS AND A PROPOSED MECHANISM

Rat hearts perfused for 60 min with hypoxic Krebs-Henseleit medium were fixed and examined by light and electron microscopy at 0, 0.5, 1, 2, 5 and 15 min after reoxygenation. The earliest structural changes seen at 0.5 to 2 min were contracture of myocardial cells with separation of sarcomere attachments to intercalated discs and Z-bands. These separations were followed by focal, and later, diffuse mitochondrial and cytoplasmic swelling. Creatine phosphokinase release from hearts could be detected by 0.5 min, but did not peak until 2 min after reoxygenation. The observed temporal sequence of events suggests that contracture of cells precedes enzyme release and massive cell swelling. It is postulated that when oxygen-supported contracture occurs, stretching and rupture of cell sarcolemmal membranes occurs in dyskinetic regions of cells left unsupported by sarcomere detachments. © 1979.