Desempenho natatório de tambaqui e matrinchã: aspectos ambientais e farmacológicos envolvendo o óxido nítrico

Abstract

Nitric oxide is produced from L-arginine by the enzyme nitric oxide synthase and is a signaling molecule with important role in cardiovascular homeostasis, neurotransmission, immune defenses, vasodilation and muscle performance, among others. Besides being the precursor of the synthesis of nitric oxide, arginine has been reported as a supplement to reduce stress and increase performance, since it increases the production of nitric oxide, increasing blood perfusion during exercise. This study aimed to verify if the muscle nitric oxide acts to delay fatigue of exercised fish. It also aims to identify whether supplementation of fish feed with arginine or L-NAME (its antagonist) can interfere with swimming performance or its resistance to stress of exercise. Both species were subjected to the following experiments: (a) incremental exercise until fatigue (ucrit); (B) prolonged and moderate exercise (30 cm/s for 12 hours); (C) hypoxia with access to the water surface; (D) hypoxia without access to the water surface; and (e) feed supplementation with arginine, L-NAME (1 g/Kg of feed) or equivalent amount of alanine to balance nitrogen, and exposure of animals to subsequent exercise. The results indicate that nitric oxide in tambaqui only rises at fatigue, and in matrinchã nitric oxyde takes place in the early stages of the swimming, helping to delay fatigue by delaying energy dependence of white muscle and the consequent accumulation of lactate. Results also indicates that feed supplementation with small amounts of arginine can not increase swimming performance in both species, but it can help in the recovery of matrinchã by allowing a better blood perfusion, and of the tambaqui, by raising the response of the cortisol to exercise.