Mechanics of patch clamped and intact cell-membranes in relation to SA channel activation.

Stretch activated (SA) channels are believed to be activated by tension in the membrane generated by membrane stretch. However, very few studies have been made on the quantitative estimation of the tension during membrane stretch. Here we present a method to evaluate the tension both in patch clamped and intact cell-membranes. The tension in patch clamped membranes was calculated from Laplace's law by knowing transmembrane pressure and the radius of patch-curvature. We also provide a simpler version for calculating the tension from the pressure and pipette radius. The tension in intact cell membranes was calculated from Hook's law based on the measurement of changes in cell surface area. The estimated tension required for activating SA channels in both types of membranes was found to be comparable suggesting that the SA channel acts as a physiological mechanotransducer in intact cells.