[The effects of dioscin on myocardial contraction and sodium-cal-cium exchanger].

OBJECTIVE: To investigate the inotropic effects of dioscin (Dio)in rat isolated-heart and intracellular free calcium concentration in isolated rat ventricular myocytes and to explore its mechanism preliminarily. METHODS: Left ventricle contractile function was measured using the Langendorff non-recirculating mode of isolated rat heart perfusion. Effects of dioscin and dioscin+SEA0400, sodium-calcium exchanger (NCX) inhibitor, were investigated by measuring left ventricular systolic pressure (LVSP) and left ventricular end diastolic pressure (LVEDP). Also, heart rate (HR), peak rate of rise/fall of left ventricular pressure (±dp/dtmax) of isolated rat heart were calculated; Effects of dioscin and SEA0400 on intracellular free calcium concentration in rat H9c2 cells were measured by Fluo3-AM and then detected the fluorescence intensity with confocal microscopy. RESULTS: With 1 μmol/L dioscin, LVSP was significantly increased by 19.7% (P<0.01) and dp/dtmax was increased by 9.6%; With 1 μmol/L dioscin, the relative fluorescence intensity of intracellular free calcium concentrations were strong significantly(P<0.01). While in presence of SEA0400, the relative fluorescence intensity was changed to 17.09±0.63 (P<0.01) by 1 μmol/L dioscin. With 1 μmol/L dioscin, the relative fluorescence intensity was weak(P<0.01) without calcium or sodium in the extracellular fluid. CONCLUSIONS: Dioscin shows positive inotropic effect on isolated rat heart, enhancing the LVSP and +dp/dtmax; Dioscin increases the intracellular concentration of Ca2+ in the cardiac myocytes by increasing Na+ influx and facilitating the reverse mode of the sodium-calcium exchanger.