Influence of variations in pericellular oxygen tension on individual cell growth,muscle-characteristic proteins,and lactate dehydrogenase isoenzyme pattern in cultures of beating rat heart cells

Summary Primary cell cultures from neonatal rat ventricles were continuously exposed for 7 days in a modified roller apparatus to defined pericellular oxygen tension varying from 0.6 to 600 mm Hg. 5-Fluorodeoxyuridine was added to the medium to prevent over-growth of muscle cells by nonmuscle cells. A pericellular pO₂ of 600 mm Hg was lethal. The range of about 15 to 150 mm Hg was favorable, as indicated by increases in total and muscle-characteristic proteins. Between the 2nd and 8th day of cultivation at a pO₂ of 38 mm Hg, myosin content per cell increased 3.2-fold and creatine kinase activity 2.5-fold. At 0.6 mm Hg, myosin content increased only 1.3-fold and there was no increase in creatine kinase activity. The rate of myosin synthesis was diminished at this low pO₂. ATP level and beating rate at 0.6 mm Hg did not differ from values at 38 mm Hg. The isoenzyme pattern of lactate dehydrogenase remained unchanged during cultivation at 38 mm Hg, whereas at 0.6 mm Hg it shifted towards an M-type pattern. These experiments suggest that neonatal rat heart cells maintained in vitro can adapt themselves to low oxygen tensions.