Ginseng–Aconite Decoction elicits a positive inotropic effect via the reverse mode Na+/Ca2+ exchanger in beating rabbit atria

Abstract

Ethnopharmacological relevanceGinseng–Aconite Decoction (GAD), a traditional oriental medicine composed of Panax ginseng C.A. Mey. (Araliaceae) and Aconitum carmichaeli Debx. (Ranunculaceae) has been used as treatment for cardiovascular diseases from Song Dynasty of China. The purpose of the present study was to elucidate the possible mechanisms of GAD-induced positive inotropic effect. Material and methodsGAD-induced changes in atrial dynamics and cAMP efflux were determined in isolated perfused beating rabbit atria. ResultsGAD significantly increased atrial dynamics such as stroke volume, pulse pressure and augmented cAMP efflux in beating rabbit atria. The inotropic effect was significantly attenuated by pre-treatment with KB-R7943, a reverse mode Na+/Ca2+ exchanger blocker. The GAD-induced increase in atrial dynamics was also markedly inhibited by staurosporine, a non-selective protein kinase inhibitor, and partly blocked by KT5720, a selective PKA inhibitor. The effect of GAD on atrial dynamics was not altered by pre-treatment with propranolol, a β-adrenergic receptor inhibitor, or diltiazem, an L-type Ca2+channel blocker. The phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine (IBMX) failed to modulate the GAD-induced increase in atrial dynamics, but markedly attenuated cAMP efflux in the beating atria. ConclusionThese results suggest that the GAD-induced positive inotropic effect in beating rabbit atria may be attributable to stimulation of the reverse mode Na+/Ca2+ exchanger, while PKA activity would, at least in part, be participated in the course.