Dimethyl Amiloride On Cardiac Hypertrophy In Rats And Normal Rats In Vitro Heart Function And Myocardial Mechanics And Mechanisms Explored

AIM:To study effects of DMA on cardiac function in hypertrophied rat isolated hearts and myocardial contractility in hypertrophied isolated rat papillary muscle of left ventricle and explore its probable mechanism. METHODS: With Langendorff perfusion, we observed changes of the indexes reflecting cardiac function in hypertrophied rat isolated hearts and compared with normal rat isolated hearts. With isolated papillary muscle perfusion, developed tention was measured to estimate the positive inotropic action of DMA on hypertrophied cardiac tissue level and compared with normal cardiac tissue. RESULTS: 1. In Langendorff-perfused hypertrophied rat hearts, DMA(0.5²μmol·L^-1)enchances cardiac function and exerts positive effects on LVSP-LVDP﹑+dp/dtmax,-dp/dtmax. 2. In hypertrophied isolated rat papillary muscle of left ventricle, DMA(0.5²μmol·L^-1)can improve developed tension. 3. In hypertrophied isolated rat hearts and papillary muscle, the effects of DMA start to present at the second minute and maximize at the fourth to sixth minute, maintain ten to twelve minutes. 4. In normal hearts and myocardium, DMA shows similar pharmacologic profile but less sensitive than in hypertrophied hearts and myocardium. 5. The effects of DMA on cardiac function in hypertrophied rat isolated hearts and myocardium inotropism in hypertrophied isolated rat papillary muscle of left ventricle cannot be blocked by nicardipine --one of calcium channel blocker,but can be blocked by NiCl2--one of sodium calcium exchanger(NCX) blockers. CONCLUSION: 1. DMA (2μmol·L^-1 and 4μmol·L^-1) can enhances systolic and diastolic function in normal and(0.5²μmol·L^-1) hypertrophiedrat isolated hearts. 2. DMA (2μmol·L^-1 and 4μmol·L^-1) exerts positive inotropic action in normal and(0.5²μmol·L^-1) hypertrophiedisolated rat papillary muscle of left ventricle. 3. The hypertrophied isolated papillary muscle and hearts are more sensitive than the normal. 4. By agitating NCX, DMA enhances cardiac function in hypertrophied rat isolated hearts and exerts positive inotropic action in hypertrophied rat papillary muscle of left ventricle, independent of L-calcium channel.