Résumé : Mechanoelectrical transduction in gramicidin A channels was studied in macroscopic planar lipid bilayer membranes bulged at constant tension. We found a supralinear increase in the single channel activity that was proportional to the square of membrane radius, but could not be accounted for by the increase in membrane surface area, or by recruitment of new channels. Extrapolated to biological membranes, these observations may suggest that the permeability of ion channels can be influenced simply by changing shape of the membrane, with or without stretching. © Nauka/Interperiodica 2006.