Acceleratory effect of ellagic acid on sarcoplasmic reticulum Ca²⁺ uptake and myocardial relaxation

Abstract

　　The effects of ellagic acid, a phenolic phytochemical contained in fruits and vegetables, on sarcoplasmic reticulum Ca²⁺ uptake and myocardial contraction were examined in mouse ventricular myocardia. In cardiomyocytes loaded with Fura-2 (a fluorescent Ca²⁺ indicator), isoprenaline (a β-adrenoceptor agonist) produced a decrease in the basal fluorescence ratio. This decrease was inhibited by propranolol (a β-adrenoceptor antagonist) and cyclopiazonic acid (a sarcoplasmic reticulum Ca²⁺-ATPase inhibitor). Ellagic acid produced a decrease in basal fluorescence ratio, which was completely inhibited by cyclopiazonic acid. In isolated myocardial tissue preparations, isoprenaline increased the contractile force and shortened the time required for relaxation. Ouabin, a cardiac glycoside, increased the contractile force but did not affect the time required for relaxation. Ellagic acid shortened the time required for relaxation but did not affect the contractile force. The beating rate of isolated right atria was increased by isoprenaline, but ellagic acid had no effect. In conclusion, ellagic acid accelerates sarcoplasmic reticulum Ca²⁺ uptake and myocardial relaxation without affecting the contractile force or the beating rate. Ellagic acid, which has such non-conventional mode of action, may be of value in the long-term maintenance of cardiac function.