Anoxia in neonatal rat heart cell cultures.

Monolayer cultures of heart cells are prepared by dissociation of neonatal rat hearts with collagenase. The regularly and synchronously contracting monolayer is subjected to oxygen and metabolic substrate deprivation for some time (anoxia), and is, in a number of experiments, followed by a short period of oxygen and metabolic substrate repletion (reoxygenation). Analysed were the frequency and regularity of beating, number of nonvital cells, and enzyme activities and DNA content in the cells as well as in the extracellular medium. We observed that a correlation exists between the released activity of a cytoplasmic enzyme, alpha-hydroxybutyrate dehydrogenase (HBDH) and i) number of nonvital cells, ii) depression of beating frequency measured during reoxygenation, iii) the released activities of enzymes from sarcolemma (L-leucylnaphthylamidase), from lysosomes (N-acetyl-beta-glucosaminidase), and mitochondrial outer membrane (monoamine oxidase). No correlation exists between the released activity of HBDH and a) the released activity of an enzyme system from the mitochondrial inner membrane (succinate: cytochrome c reductase), and b) the released amount of DNA. Furthermore, reoxygenation of anoxic heart cell cultures leads to a suddenly occurring HBDH release which phenomenon is known as "oxygen paradox".