Aqueous fraction from Costus spiralis (Jacq.) Roscoe leaf reduces contractility by impairing the calcium inward current in the mammalian myocardium

AqF from Costus spiralis reduces the calcium entry in myocardial cells as showed by its effect on the Bowditch phenomenon and on the positive inotropic effect produced by both BAY K8644 and isoproterenol. Direct measurements of the L-type calcium current (ICa, L) as well as of the intracellular free calcium determined by the fluorescence of FLUO 4AM (F/F0) confirmed such hypothesis.