Effects of methane on proximal colon motility of rats and ion channel mechanisms

Objective To explore the effects of methane on proximal colon motility and elucidate its ion channel mechanisms. Methods The circular muscle and longitudinal muscle strips of proximal colon were isolated from rats.An isometric force transducer and a biology signal collection system were employed to observe the effects of methane on spontaneous contractile activity of muscle strips.The effects of methane on longitudinal muscle strips were observed after pre-treatment of these strips with tetrodotoxin (TTX) or N-nitro-L-arginine methylester (L-NAME).Single cell of colonic smooth muscle was isolated by collagenase and then whole-cell patch clamp technique was used to record voltage dependent potassium current (IKV) and large conductance Ca2+-activated K+ current (IBKca) in the absence or presence of methane. Results Methane significantly attenuated the contractile amplitude of longitudinal muscle strips (from (1.12±0.27) to (0.99±0.31) g, n=19, P=0.013) whereas there were no changes in some longitudinal muscle strips (n=6) in the presence of methane.The inhibitory effect of methane persisted after the pre-treatment of longitudinal muscle strips with TTX or L-NAME.Methane had no effects on the contractile cycle time of longitudinal muscle strips and contractile activity of circular muscle strips.And 3% methane solution significantly increased the density of IKV (from (13.3±1.0) pA/pF to (18.5±1.4) pA/pF, at +60 mV, n=11, P=0.001) versus the control group whereas methane had no effect on IBKca (all P>0.05). Conclusion Methane can inhibit contractile activity of proximal colonic longitudinal muscle by activating voltage dependent potassium channel and increasing IK V. Key words: Methane; Patch-clamp techniques; Voltage-dependent potassium channels