Abstract: Objective To study the expression and mechanosensitivity of ATP-sensitive potassium channel(K_ATP) in rat colonic smooth muscle cells.Methods Reverse transcription polymerase chain reaction(RT-PCR) was used to measure mRNA expression of K_ATP in colonic smooth muscle.K_ATP channel activities were investigated with patch-clamp techniques and pressure-clamp techniques in inside-out mode on isolated smooth muscle myocytes.Results RT-PCR amplified the expected product of 727 bp for K_ATP from total RNA isolated from colonic smooth muscle.In this mode,K_ATP activities were recorded on isolated smooth muscle cells,the mean conductance was(44.5±1.5)pS at +60 mV.The activities were blocked by glibenclamide(10 μmol).The open probability of K_ATP channels was increased by-40 mmHg suction pressure.Conclusion K_ATP channels are expressed in rat colonic smooth muscle cells and are sensitive to stretch stimuli.These results suggest that the channel may be involved in the regulation of electric and mechanic activities of colonic smooth muscle in rats.

Key words: K_ATP channels, mechanosensitivity, colonic smooth muscle