The present study investigates the antioxidant activity of A.V. Circulo (AVC), a polyherbal formulation in isoproterenol(ISO)-induced oxidative stress in rats and attempts to correlate its cardioprotective activity with antioxidant activity. Myocardial necrosis was produced in rats with ISO (85 mg/kg, s.c.), injected twice at an interval of 24 h. AVC (500 mg/kg, p.o.) was administered to rats for 21 days and 45 days and its effect was evaluated on ISO-induced cardiac injury. The marker enzymes - AST, LDH & CPK were assayed in serum and heart, and antioxidant parameters, viz., reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) & glutathione reductase (GR), and malondialdehyde (MDA), were determined in heart homogenate. Significant myocardial necrosis, depletion of endogenous antioxidants and an increase in serum levels of marker enzymes were observed in ISO-treated rats when compared with normal rats. Daily pretreatment of AVC (500 mg/kg) for 21 & 45 days to rats which were treated with ISO on the last 2 days, resulted in a significant cardioprotective and antioxidant activity, reflected by decreased levels of serum marker enzymes & MDA, and restored activities of marker enzymes, GSH, and antioxidant enzymes in the heart. AVC (500 mg/kg) administration for 45 days showed greater cardiac protection than for 21 days. It is concluded that AVC (500 mg/kg) oral treatment for 21 & 45 days to ISO-challenged rats augments endogenous antioxidant enzymes in the rat heart and prevents lipid peroxidation of the membrane, thereby salvaging the myocardium from the deleterious effects of ISO.
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