Stretch-activated whole cell currents in adult rat cardiac myocytes

Mechanoelectric transduction can initiate cardiac arrhythmias. To examine t he origins of this effect at the cellular level, we made whole cell voltage -clamp recordings from acutely isolated rat ventricular myocytes under cont rolled strain. Longitudinal stretch elicited noninactivating inward cationi c currents that increased the action potential duration. These stretch-acti vated currents could be blocked by 100 mu M Gd3+ but not by octanol. The cu rrent-voltage relationship was nearly linear, with a reversal potential of approximately -6 mV in normal Tyrode solution. Current density varied with sarcomere length (SL) according to I (pA/pF) = 8.3 - 5.0SL (mu m). Repeated attempts to record single channel currents from stretch-activated ion chan nels failed, in accord with the absence of such data from the literature. T he inability to record single channel currents may be a result of channels being located on internal membranes such as the T tubules or, possibly, ina ctivation of the channels by the mechanics of patch formation.