Tribulus terrestris protects rat myocardium against isoproterenol-induced ischemic injury: role of HSP 70 and cardiac endogenous antioxidants

The present study was undertaken to evaluate the cardioprotective activity of Tribulus terrestris (Tt), a medicinal herb following isoproterenol (ISP)-induced myocardial injury. The contribution of heat shock protein (HSP) 70, key anti-stress protein, endogenous antioxidants and oxidant -antioxidant balance in attenuating myocardial injury was further studied. Hydroalcoholic extract of Tt {1, 2.5, 5 & 10 mg/kg} were orally fed once a daily to Wistar rats for 21 days. On the 20th and 21st day, both control (ISP control) and Tt fed rats were challenged with ISP (85 mg/ kg, s. c. two doses at 24h intervals) induced myocardial necrosis. Histopathological evaluation, cardiac marker enzyme: Creatinine phospho - kinase(CPK) and antioxidative parameters: Glutathione (GSH), Thiobarbituric acid reactive substances (TBARS), Catalase (CAT), Glutathione peroxidase (GSHPx) and Superoxide dismutase (SOD) levels were estimated. Tt (2.5 mg/kg) intake per se upregulated HSP 70; increased basal SOD, CAT activity (P<0.05) and caused a marked fall in basal TBARS levels (P<0.05) in comparison to sham. Following ISP challenge, significant oxidative stress with evidence of myocardial necrosis was observed in the ISP control group. ISPinduced changes in myocardial SOD, GSHPx and GSH were prevented by both the 2.5 and 10 mg/kg doses of Tt, though cellular injury was minimal with 2.5 mg/kg dose. The results emphasize that pre-treatment with Tt offered significant protection against ISP-induced myocardial necrosis through a unique property of enhancement of endogenous antioxidants, stabilization of cytoskeleton structure which in turn is attributed to HSP 70 expression along with fortified antioxidant defense system.