Effect of exposure to sublethal levels of potassium cyanide on serum and tissue enzymes in roach fish (Rutilus rutilus). Onl J Vet Res., The effect of a 30 day exposure of 0.2 and 0.4 mg/L potassium cyanide (KCN) on the levels of serum and tissue enzymes of the common roach fish Rutilus rutilus is described. Results were compared with non-exposed fish. Alkaline phosphatase (ALT) increased in all examined tissues and serum. Aspartate aminotransferase (AST) activity was elevated in liver, kidney, gill and serum in fish exposed to 0.4 mg/L KCN. In contrast, AST in brain tissue was reduced with exposure to 0.2 mg/L KCN. Lactate dehydrogenase (LDH) level were reduced in kidney and brain compared with non-exposed controls whereas liver and serum LDH activity was enhanced at both KCN concentration. Serum, brain and gill ALT increased at higher KCN exposures. Rhodanese activity enhanced significantly in liver and kidney at both cyanide concentrations (p<0.05) but it showed no significant difference in gill of roach (p>0.05). Key words: Cyanide, poisoning, Rutilus rutilus, tissue enzyme INTRODUCTION

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