Introduction: In toxicological studies, the alterations in the enzymatic activities directly reflect the metabolic disturbances and cell damage in specific organs. The aim of the current study was to determine the effects of lead exposure on tissue enzyme activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) in selected tissues of common carp and also to evaluate the beneficial effects of allicin, the main active constituent of garlic, on modulating enzyme alterations. Methods: Common carp (Cyprinus carpio; total, n=60) were divided randomly into three groups of 20 each. Group I fish were reared in normal freshwater and served as the control. Group II fish were exposed to lead acetate (7.0 mg L−1) for 10 days. Group III fish were exposed to lead acetate (7.0 mg L−1) for 10 days and also received dietary allicin (10 mg/kg body weight, daily) during lead acetate treatment. At the end of each exposure, enzyme activities in prepared tissue homogenates were determined using colorimetric methods. Results: Lead exposure caused a significant elevation of AST, ALT and LDH in the liver, as compared to control group (P<0.05). The AST, ALT, ALP and LDH levels in kidney homogenates were considerably increased following lead exposure, although these increases were only significant for ALT and ALP values. Significant increases of brain ALT and gill ALP activities were also observed following lead exposure. However, alterations in the activities of other measured enzymes in both brain and gill of experimental groups were not significant. Conclusion: Allicin supplementation was effective in attenuating the increase in Pb-induced tissue enzyme activities in the most organs; therefore it might have some protective and therapeutic effects on lead poisoning. However, much more extensive biochemical and toxicological research are needed for better understanding of the molecular basis of lead induced tissue enzyme alterations and ameliorative properties of allicin.

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