Effect of Astragalosides on Intracellular Calcium Overload in Cultured Cardiac Myocytes of Neonatal Rats

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Abstract
Astragalosides were the main active components from a native Chinese herb Astragalus membranaceus. Recent studies have shown that Astragalosides have a protective effect on myocardial injury in rats. The present study was designed to investigate the effect of Astragalosides on intracellular calcium overload and sarcoplasmic reticulum calcium load (SR Ca 2+ load) in cultured cardiac myocytes from neonatal rats. Astragalosides (100 μg/ml) were incubated in the presence of isoproterenol (ISO) (10-5 M) for 72 hours in cardiomyocytes. Metoprorol (10-6 M), a β1-selective antagonist, was cultured in the same condition as Astragalosides. The result showed that intracellular calcium concentration ([ Ca 2+] i ) and SR Ca 2+ load increased in ISO-treated cardiac myocytes as compared to control (P2+] i and SR Ca 2+ load. Metoprolol also inhibited those increase. The mRNA expression and activity of sarcoplasmic reticulum Ca 2+ ATPase (SERCA) were enhanced following ISO treatment in cardiac myocytes, and these increases were inhibited by Astragalosides or metoprolol (P2+] i and SR Ca 2+ load, enhancing free radical removal and decreasing lipid peroxidation in ISO-treated cardiomyocytes, which might account for their protective effect on myocardial injury.