Ion selectivity of stretch-activated cation currents in mouse ventricular myocytes

Stretch-activated non-selective cation currents ( I(SAC)) constitute a mechanism that can induce cardiac arrhythmias. We studied I(SAC) in mouse ventricular myocytes by stretching part of the cell surface between the patch-pipette and a motor-driven glass stylus. In non-clamped cells, local stretch depolarised and induced after-depolarisations and extrasystoles. In voltage-clamped cells (K(+) currents suppressed) I(SAC) activated by local stretch had a nearly linear voltage dependence and reversed polarity between -12 and 0 mV. Conductance G(SAC) increased with the extent of local stretch. I(SAC) was not a Cl(-) current (insensitivity to replacement of Cl(-) by aspartate(-)). I(SAC) was not a Ca(2+)-activated current (insensitivity to 5 mM intracellular BAPTA). G(SAC) was blocked by 5 micro M GdCl(3) or by 75 mM extracellular (e.c.) CaCl(2). Removal of e.c. CaCl(2) increased G(SAC) 2.5-fold, as if G(SAC) were sensitive to Ca(2+) and Gd(3+). Replacement of 150 mM e.c. Na(+) by 150 mM Cs(+), Li(+), tetraethylammonium (TEA(+)) or N-methyl d-glucosamine (NMDG(+)) yielded currents that suggested for the conductance a selectivity G(Cs)> G(Na)> G(Li)> G(TEA)> G(NMDG). I(SAC) was suppressed by cytochalasin D, as if an intact F-actin cytoskeleton were necessary for activation of I(SAC).