Effect of acute exercise on tissue free fatty acids in untrained rats

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Abstract
The effects of a single bout of swimming on free fatty acids (FFA) in adipose tissue, heart, skeletal muscle, and serum were examined. Surprisingly, in previously untrained rats, FFA were elevated (P < 0.001) in epididymal, inguinal, and retroperitoneal adipose depots 48 h after a 2-h swim. FFA in the three fat depots returned to resting levels 96 h after exercise. In heart, soleus, and fast-red fibers of the quadriceps, FFA remained elevated (P < 0.01) for as long as 72 h after the 2-h swim. Serum FFA were still elevated (P < 0.001) 96 h after swimming but not after 168 h. These results provide evidence that the rise in FFA is an acute effect of exercise and not a cellular adaptation resulting from daily episodes of lipolysis induced by exercise training. In a separate experiment, involving the adaptive response to endurance exercise, adipocytes from epididymal, inguinal, and retroperitoneal depots were reduced in size (P < 0.001) to approximately the same degree. These results provide evidence that adipocytes from each depot contribute equally in meeting the energy needs of muscle during repeated bouts of endurance exercise.