Effects of mechanical activity and hormones on myocardial glucose and fatty acid utilization.

The effects of increased cardiac work on glycolysis, the citric acid cycle, and oxidation of fatty acids were studied in isolated rat hearts. Glycolysis was stimulated by increased work in heart perfused with glucose alone or with glucose, high levels of insulin, and low levels of palmitate. With glucose alone, stimulation was associated with a rapid decrease in phosphate potential and rapid activation of phosphofructokinase, but an apparently slower activation of glucose transport. With glucose, insulin, and palmitate present, stimulation of glucose utilization was rapid and correlated with activation of phosphofructokinase.