Influência do treino físico, de predomínio excêntrico, na tolerância ao dano induzido por cardiotoxina e nos subsequentes mecanismos de reparação muscular. Estudo em modelo animal.

Abstract

Regular physical exercise of eccentric predominance induces muscular adaptations capable of promoting tolerance to the same type of exercise performed later, a phenomenon known as physical preconditioning. However, although these effects are well documented, there is little evidence regarding a hypothetical cross-tolerance to stimuli of another nature and its influence on the repair process when skeletal muscle is subjected to damage other than exercise. Objective: to evaluate the effects of eccentric predominance physical exercise on tolerance to future cardiotoxin-induced damage and on the tibialis anterior muscle repair process, namely: i) the magnitude of the inflammatory response, ii) the quality of the regenerative response iii) the intensity of the healing response. Material and Methods: 50 male Wistar rats, 4.5 months old, randomly distributed into a sedentary group (n = 25) and a trained group (n = 25) were used. The animals of the trained group performed a running training protocol on a treadmill (-25º; 30m / minute; 60 minutes) once a week, for 9 weeks. One week after the training protocol, all the animals were injected with cardiotoxin in the right tibialis anterior muscle and with saline solution in the left tibialis anterior muscle, and five animals from each group were subsequently euthanized after 1, 3, 7, 14 and 21 days. The muscles were processed for further morphological and immunohistochemical analysis using optical microscopy. Results: the training protocol did not induce cross-tolerance to the damage induced by cardiotoxin, since the total damage was equally intense in both groups, although more quickly resolved in the trained group. The inflammatory response to the damage, although intense in the first moments, quickly returned to normal values in the trained group. Muscle repair in the trained group was essentially promoted by the regeneration process and not by the healing process. Conclusion: although exhaustive exercise did not promote tolerance to the acute damage induced by cardiotoxin, it benefited the muscle repair process, with the inflammatory response being more quickly attenuated and the regenerative response being prevalent than the cicatricial one, with faster muscle repair when compared to the group of animals that did not undergo the training protocol. KEY-WORDS: PHYSICAL EXERCISE, PRECONDITIONING, PROTECTION, REGENERATION, HEALING PROCESS, TIBIALIS ANTERIOR MUSCLE, HISTOLOGY.