ABSTRACT
OBJECTIVE: To observe whether low concentration (1×10-8 mol·L-1) of ouabain (OUA) can increase the contractility in rat cardiocytes and investigate the Na/K pump signal transduction pathways related to positive inotropic action following the low concentration of OUA. METHODS: On enzymatic isolation of rats ventricular myocytes, the Na+/K+ pump current (Ip) was by whole-cell patch-clamp, in order to observe the low concentration of OUA on Ip. The contraction of a single myocyte was assessed by a video-based motion edge-detection system. (1) To detect and compare the potentiations of 1×10-8-1×10-3 mol·L-1 OUA on the contractility in rat cardiocytes. (2) The cardiocytes were pre-treated with PP2 (1 μmol·L-1), NAC (100 μmol·L-1), PD98059(50 μmol·L-1) for 5 min, and the effects of the signals transduction inhibitors on the positive inotropic effect of 1×10-8 mol·L-1 OUA was recorded. RESULTS: The 1×10-8-1×10-3 mol·L-1 OUA increased the contractility of rat cardiocytes (P0.05). CONCLUSION: The 1×10-8-1×10-3 mol·L-1 OUA could increase the contraction amplitude of cardiocytes in rats in concentration-dependent manner. Positive inotropic effect of OUA in low concentration is related to Na/K pump signal transduction. Multiple signal pathways regulate the positive inotropic effect of 1×10-8 mol·L-1 of OUA, including the Src/ROS signal pathway.