RESUMEN
The metabolic responses of Hoplias malabaricus to hypoxia caused by nitrite exposure was studied and compared to previous data of hypoxia caused by low environmental oxygen concentrations. These metabolic responses were analyzed from the contents of glycogen, glucose, lactate and pyruvate in liver, red and white muscle, heart and plasma. Glycogen mobilization provided clues to explain the metabolic behavior of the organism against internal hypoxia. The ratio of closely related metabolic intermediates was used to analyze its reaction displacement. The results permit us to conclude that H. malabaricus responds to nitrite hypoxia in the same way as when exposed to low oxygen external levels. That means hydrolyxis of hepatic glycogen followed by its synthesis in white muscle. Metabolism in the heart muscle seems to be more intense than in red muscle. Although internal and external hypoxia presented similar metabolic responses, the signiificance of this strategy remains uncertain.