Behavior of nonselective cation channels and large-conductance Ca2+-activated K+ channels induced by dynamic changes in membrane stretch in cultured smooth muscle cells of human coronary artery

INTRODUCTION: The effects of membrane stretch on ion channels were investigated in cultured smooth muscle cells of human coronary artery. METHODS AND RESULTS: In the cell-attached configuration, membrane stretch with negative pressure induced two types of stretch-activated (SA) ion channels: a nonselective cation channel and a large-conductance Ca2+-activated K+ (BK(Ca)) channel. The single-channel conductances of SA cation and BK(Ca) channels were 26 and 203 pS, respectively. To elucidate the mechanism of activation of these SA channels and to minimize mechanical disruption, a sinusoidal change in pipette pressure was applied to the on-cell membrane patch. During dynamic changes in pipette pressure, increases in SA cation channel activity was found to coincide with increases in BK(Ca) channel activity. In the continued presence of cyclic stretch, the activity of SA cation channels gradually diminished. However, after termination of cyclic stretch, BK(Ca) channel activity was greatly enhanced, but the activity of SA cation channels disappeared. CONCLUSION: This study is the first to demonstrate that the behavior of SA cation and BK(Ca) channels in coronary smooth muscle cells is differentially susceptible to dynamic changes in membrane tension.