Effects of training and of acute exercise in trained rats

Abstract

Three groups of rats were studied. Two groups of rats were trained by running for 2 mo. One group served as trained resting controls (T), the other group was given exercise immediately before sacrifice (T+E), the third group served as untrained resting controls (C). In plasma the concentration of free fatty acids (FFA) and glycerol was decreased in trained (T) compared to untrained rats (C) at rest. Training also lowered the content of triglycerides in the liver and the concentration of triglycerides in myocardium and skeletal muscle tissue. In exercised rats (T+E), the concentration of triglycerides was lowered in plasma and red skeletal muscle tissue; the content of triglycerides in the liver increased. The results indicate that training influenced the mechanisms regulating metabolism of triglyceride fatty acids in tissues at rest. The possibility that reduced availability of plasma FFA for esterification was responsible for the lowered triglyceride “pools” in tissue was discussed. It was suggested that training adapted the lipid metabolism toward increased utilization of circulating fatty acids and decreased the role of endogenous muscle triglycerides as a source for fatty acids during exercise. Training also lowered the blood glucose concentration, which was further reduced during exercise.