MECHANICS OF PATCH CLAMPED AND INTACT CELL-MEMBRANES IN RELATION TO SA CHANNEL ACTIVATION

Stretch activated (SA) channels are believed to be activated by tensio n in the membrane generated by membrane stretch. However, very few stu dies have been made on the quantitative estimation of the tension duri ng 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 transme mbrane pressure and the radius of patch-curvature. We also provide a s impler version for calculating the tension from the pressure and pipet te radius. The tension in intact cell membranes was calculated from Ho ok's law based on the measurement of changes in cell surface area. The estimated tension required for activating SA channels in both types o f membranes was found to be comparable suggesting that,the SA channel acts as a physiological mechanotransducer in intact cells.