Mechanisms underlying the cardioprotective effect of Salvianic acid A against isoproterenol-induced myocardial ischemia injury in rats: Possible involvement of L-type calcium channels and myocardial contractility

Abstract Ethnopharmacological relevance Salvianic acid A (SAA), which is the main water-soluble fraction in Radix Salviae Milthiorrhizae , has been widely applied for treating cardiovascular diseases in China. Aim of the study To explore the effects of SAA against myocardial ischemia injury induced by isoproterenol (ISO) in rats and to clarify its underlying myocardial protective mechanisms based on l -type calcium channels and myocardial contractility. Materials and methods The myocardial ischemia injured rat model was induced by administering ISO (85 mg/kg) subcutaneously at evenly spaced intervals throughout the day and night for 2 consecutive days. Serum cardiac biomarkers were analyzed, and heart tissues were isolated and prepared for histopathology assay. The regulatory effects of SAA on the L-type calcium current (I Ca-L ) in rat ventricular myocytes were observed by the patch clamp technique. The IonOptix Myocam detection system was used to observe the contractility of isolated rat ventricular myocytes. Results SAA significantly ameliorated changes in heart morphology and electrocardiographic patterns and reduced serum levels of creatine kinase and lactate dehydrogenase in the ISO-induced myocardial ischemia injured rat model. Meanwhile, SAA reduced I Ca-L in a concentration-time dependent way with an IC 50 of 1.47×10 −5  M, upshifted the current-voltage, activation, and inactivation curves of I Ca-L , and significantly inhibited the amplitude of the cell shortening. Conclusions These results indicate that SAA exhibits significant cardioprotective effects against the ISO-induced myocardial ischemia injury, potentially through inhibiting I Ca-L and decreasing myocardial contractility.