Factors influencing enzyme release from cultured fetal mouse hearts deprived of oxygen and glucose

Abstract

Factors influencing the release of lactic dehydrogenase, one marker of cell necrosis, from cultured fetal mouse hearts deprived of oxygen and glucose were determined. During the 4 h of oxygen and glucose deprivation, there was no significant release of lactate dehydrogenase; however, during 24 h of resupply of oxygen and glucose, lactate dehydrogenase release from deprived hearts was significant. Lactate dehydrogenase release from hearts deprived for 3 h at 42° was 101 ± 13 miu/mg wet weight or approximately 60% of the total heart content; release from hearts deprived for 4 h at 37° was 56 ± 11 miu/mg wet weight or approximately 30% of the total. When the temperature during deprivation was decreased to 4° or 24°, no significant release occurred. Important differences depending on developmental age were demonstrated: large (3 mg) hearts lost more lactate dehydrogenase and had lower ATP and enzyme (creatine kinase and lactate dehydrogenase) contents for insults of the same duration than did the small (<3 mg) hearts. There was an inverse relationship between the lactate dehydrogenase release and the ATP content of the hearts at the end of the period of recovery: lactate dehydrogenase (miu/mg wet weight) = −1.64 ATP content (nmol/mg protein) + 63.7, n = 36, r = −0.81. The relationship of lactate dehydrogenase release to mechanical activity was examined: None of the 14 hearts that released the most lactate dehydrogenase resumed beating while hearts that resumed beating had less lactate dehydrogenase release and higher ATP content. We conclude (1) that enzyme release occurs only during reoxygenation and that extensive release can occur by passive diffusion, (2) that the amount of enzyme release is increased by prolonging the period of oxygen and glucose deprivation or by hyperthermia, and (3) that beating is not a necessary factor for enzyme release.