Effect of nitrite exposure on metabolic response in the freshwater prawn Macrobrachium nipponense

The metabolic response of the freshwater prawn, Macrobrachium nipponense to nitrite toxicity was evaluated. The prawns were exposed to 0, 1, 2, 3 and 4 mg L⁻¹ NO₂-N concentrations for 48 h. The metabolic parameters in muscle were measured after 12, 24 and 48 h. Glucose level significantly increased after 24 h. Exposure to lower nitrite concentrations (1 and 2 mg L⁻¹) resulted in significant increases in alanine aminotransferase (ALT) activities after 24 and 48 h. Aspartate aminotransferase (AST) activities treated with 2 and 3 mg L⁻¹ nitrite-N at 48 h were significantly higher than those at 12 and 24 h. Intermediate sublethal nitrite concentrations produced significant elevations in lactate dehydrogenase (LDH) activities from 12 h up to 48 h. No significant changes were detected in any of the groups for triglycerides and creatine kinase (CK). To satisfy the increased energy demands caused by acute nitrite exposure, mobilization of lipids is not the main reason while utilization of amino acids seems to play a more important role. The results would be helpful for aquaculture farmers to prevent a potential depression of productivity caused by elevated nitrite levels.