Interrelation between carbohydrate and fatty acid metabolism of isolated perfused rat heart

The metabolic interrelationships of carbohydrate and fatty acid metabolism in the perfused rat heart were studied. Palmitale consistently reduced the oxidation of glucose-U-C 14; this effect was associated with less glycogen breakdown, more incorporation of glucose label into glycogen and, in some instances, more lactate formation. Acetate and pyruvate had similar effects but also reduced the glucose uptake. The oxidation of palmitate-1-C 14 was not decreased by the presence of glucose or pyruvate; acetate did not alter the uptake but reduced the oxidation of palmitate and increased the fraction recovered in tissue triglyceride. The results showed that free fatty acids were oxidized in preference to glucose, and suggested a controlling effect of fatty acids on glucose metabolism. The observed effects of palmitate, acetate and pyruvate on glucose-U-C 14 metabolism supported the hypothesis that their inhibition of glucose oxidation occurred, in part, at the pyruvate-acetyl Co-A level.