Ação central do lactato no metabolismo de amônia durante o exercício físico

Abstract

During exercise, the increase in the production of ammonia is a combined effect of both the deamination of purine nucleotides as catabolism of amino acids. The values of ammonia concentration reached during exercise are extremely high when compared with the values at rest and can increase up to 100%. Therefore, this study tried to explain why this increase can occur without compromising the functioning of the organs. The issue is relevant because, during exercise, the ammonia concentration reaches 150 M; if an individual presented this ammonia concentration at rest, that hyperammonemia would be considered a pathological state. It is speculated that lactate is essential to protect the organism from the excess ammonia, influencing the metabolism of nitrogenous compounds. To test the hypothesis, we used adult male Wistar rats weighing 300 g. The rats were submitted to the implantations of a cerebral guide cannula and of a cannula into the jugular vein. After recovery from surgery, the animals were submitted to the experimental conditions: the exercise speed of 21 m.min-1 or 60 minutes of rest in their cage at a room temperature of 25 C. Each animal was subjected to four experimental conditions with 48-hour interval: central injection of saline, or ammonia, or lactate or ammonia more lactate. We found a higher concentration of lactate and ammonia in the group that underwent the exercise compared to the rest. The ICV injection caused an increase in lactate concentration in minute 15 minute (4.4 ± 0.2 mM) and in the voluntary interruption of effort (5.4 ± 0.2 mM) compared to the control situation (15 min 3.3 ± 0.3 mM, P = 0.01; IVE 4.3 ± 0.3 mM, P = 0.007), the ammonia situation (15 min 3.5 ± 0.2 mM, P = 0.002; IVE 3.2 ± 0.2 mM, P 0.001) and ammonia plus lactate situation (15 min 3.6 ± 0.3 mM, P = 0.04; IVE 3.9 ± 0.3 mM, P 0.001) and a lower concentration of ammonia in minute 5 and in the voluntary interruption of effort compared to the control situation (min 5 P = 0,02; IVE P 0.001). Thus, the ammonia concentration in the voluntary interruption of effort in rats did not differ from those found in pathological cases, but there was no damage to the organism, since the lactate reduced the effects of hyperammonemia.