Abstract: Objective To examine whether stretching of rat left ventricles has any effect on the rat cardiac electric activity and to observe whether stretch-activated ion channels(SACs) play a role in this process by using the blocker in order to reveal the possible mechanisms of cardiac mechano-electric feedback(MEF).Methods Electrocardiogram(ECG) of rat was recorded. The pressure in the left ventricle was controlled by using pressure clamp technique. Extra-stretch was applied at the end of diastole by the pressure clamp to observe whether there would be any effect on the rat cardiac electric activity. Streptomycin(800 μmol/L), a non-specific blocker of stretch-activated non-selective cation channels(SACCs) was perfused for 30 min and the alterations of the effect of the mechanic stimulus were observed to identify the mechanism of cardiac MEF.Results There was no alteration in the cardiac electric activity when left ventricular pressure(LVP) was clamped at 0 mmHg or with a normal pressure waveform. Application of stretch(140 mmHg, 30 ms) at the end of diastole caused premature ventricular excitations (PVEs). After perfusion of streptomycin(800 μmol/L) for 30 min, the PVE caused by the extra-stretch disappeared.Conclusion Strong extra-stretch applied at the end of diastole can induce alterations of cardiac electric activity, which indicates that depolarization currents were activated by the stretch. Streptomycin can block this effect, which indicates stretch-activated non-selective cation channels are involved in cardiac MEF.

Key words: mechano-electric feedback, stretch, streptomycin, stretch-activated non-selective cation channels, pressure clamp