In vitro studies of beating-heart cells in culture. XI. The ATP level and contractions of the heart cells

Abstract

1. The beating of heart cells in tissue culture is not affected by the inhibition of either glycolysis or oxidative phosphorylation alone. When both pathways are inhibited simultaneously, beating stops. 2. The ATP concentration does not change significantly when either glycolysis or oxidative phosphorylation is inhibited alone. When both glycolytic and oxidative phosphorylation inhibitors are present, the ATP level drops significantly. The combined effect of both inhibitors exceeds the sum of the effects of the individual inhibitors. 3. Dinitrophenol inhibits the beating of heart cells with a concomitant small decrease in ATP level. The addition of oligomycin restores the ATP level to control values and beating resumes. 4. Heart cells in which beating is inhibited, respond to electrical stimulation, even though the ability to beat spontaneously has been lost. Contractions in response to stimulation can be observed until the decrease of ATP has reached 85–90%. 5. It is concluded that heart cells must have a mechanism for maintaining a high steady-state level of ATP, since such a high level is required for spontaneous beating. The possible mechanisms for the maintenance of high steady-state level of ATP are discussed.