Effect of exercise on FFA metabolism of pancreatectomized dogs

Abstract

Normal and pancreatectomized dogs with indwelling arterial and venous catheters were exercised on the treadmill for 35 min. Palmitate-1-C 14 was infused intravenously for 3 hr during the experiment, or administered orally 15 hr before the experiment. The plasma free fatty acid (FFA) level was decreased in normal dogs but increased in the pancreatectomized animals during exercise. This was due to corresponding changes in the rate of FFA release. The rate of uptake of plasma FFA followed the rate of release with some delay, so that at the end of exercise the uptake was tenfold higher in the pancreatectomized dogs than in the controls. In spite of this striking difference, the C 14 O 2 output was increased during exercise four- to fivefold in both groups in the infusion experiments. When the radiopalmitate was administered orally, however, the specific activity of the exhaled C 14 O 2 rapidly decreased in the exercising pancreatectomized dogs but remained rather constant in the controls. It is suggested that during heavy exercise the muscles of the normal dog oxidize their endogenous fat pools, whereas the pancreatectomized animal relies for fat oxidation on the plasma FFA, the concentration of which is considerably increased by norepinephrine in the absence of insulin.