Experiments were designed to study in-vivo effects of sodium cyanide on biochemical endpoints in the freshwater fish Labeo rohita. Fish were exposed to two sublethal concentrations (0.106 and 0.064mg/L) for a period of 15 days. Levels of glycogen, pyruvate, lactate and the enzymatic activities of lactate dehydrogenase (LDH), succinate dehydrogenase (SDH), glucose-6-phosphate dehydrogenase (G6PDH), phosphorylase, alkaline phosphatase (ALP), acid phosphatase (AcP) were assessed in different tissues (liver, muscle and gills). Result indicated a steady decrease in glycogen, pyruvate, SDH, ALP and AcP activity with a concomitant increase in the lactate, phosphorylase, LDH and G6PD activity in all selected tissues. The alterations in all the above biochemical parameters were significantly (p<0.05) time and dose dependent. In all the above parameters, liver pointing out the intensity of cyanide intoxication compare to muscle and gills. Study revealed change in the metabolic energy by means of altered metabolic profile of the fish. Further, these observations indicated that even sublethal concentrations of sodium cyanide might not be fully devoid of deleterious influence on metabolism in L. rohita.

Sublethal toxicity of cyanide to freshwater fish, Cirrhinus mrigala was evaluated to determine its effect on the activities of some antioxidative enzymes. Changes in succinate dehydrogenase (SDH), lactate dehydrogenase (LDH) and glucose-6-phosphate dehydrogenase (G6-PDH) were observed in tissues of the tested animal. Cyanide significantly decreased the activity of SDH, and G6-PDH in the liver, gill and brain tissues of the fish. The elevation of LDH indicated metabolic disorders and a clear response against energy depletion. Changes in the dehydrogenase activity in cyanide treated fish tissues may be due to fluctuations in oxidative metabolism. It is concluded that the cyanide intoxication exerted a profound impact on the enzymatic activity of the fish, as observed in the hitherto study.