Effects of potassium-aspartate salt administration on glycogen use in the rat during a swimming stress

The ergogenic effect of aspartate salts on performance during prolonged exercise is still controversial. Potential mechanisms of the suggested ergogenic effect of aspartate on exercise performance are a sparing of muscle glycogen stores or its faster resynthesis during exercise. The purpose of this study was to determine whether aspartate causes a sparing of muscle glycogen during exercise. Six groups of rats were studied: one group received a single injection of aspartate (1 g.kg-1, IP) and was then sacrificed at rest, a second group of aspartate-treated rats was sacrificed after a 60-min swim. The third and fourth groups were given an injection of physiological saline and then sacrificed respectively at rest and after a 60-min swim. The fifth and sixth groups were given an aspartate or a saline injection and then sacrificed after swimming to exhaustion. The exhaustion times after saline (178.9 +/- 38.2 min) and aspartate (174.4 +/- 45.2 min) were not significantly different. Results did not confirm an ergogenic effect of a single dose of aspartate on swimming endurance in the rat. Aspartate-treated rats had a significantly lower plasma FFA concentration after swimming to exhaustion when compared to control rats (respectively, 0.70 +/- 0.25 vs. 1.16 +/- 0.45 mM). Also, the results of the present study do not support the hypothesis of a sparing of muscle or liver glycogen with aspartate, because a similar content of glycogen remained in the muscles and liver of control rats after a 60-min swim or after swimming to exhaustion.