A mechanosensitive calcium channel in human intestinal smooth muscle cells

Background & Aims: Gastrointestinal smooth muscle strips devoid of enteric nerve cells can contract in response to stretch, suggesting that mechanosen sitivity and mechanotransduction can occur at the level of the smooth muscl e cell. The aim of this study was to determine whether stretch-activated ca lcium channels are present in gastrointestinal smooth muscle cells. Methods : Whole-cell and single-channel calcium currents were measured from human j ejunal circular smooth muscle cells in response to increased intracellular pressure, bath perfusion, and membrane stretch. Results: At 10 mm Hg positi ve pressure, peak calcium current increased from -36 +/- 10 pA to -53 +/- 1 3 pA. Bath perfusion at 10 mL/min increased calcium current from -97.7 +/- 14 pA to -122 +/- 16 pA. Single-channel open probability increased in respo nse to negative pipette pressure. All increases were blocked by nifedipine. Conclusions: A stretch-activated, nifedipine-sensitive calcium channel is present in human jejunal circular smooth muscle cells. The channel is activ ated by both an increase in intracellular pressure and by external shear fo rces. The presence of a stretch-activated Calcium channel in gastrointestin al smooth muscle cells may allow the smooth muscle cells to act directly as mechanotransducers and to participate in the regulation of smooth muscle t one and intestinal motility.