The Role of Calcium-activated Potassium Channels in the EDHF-mediated Endothelium-dependentVasodilatation

Objective The present study was designed to explore the role of K_Ca in the EDHF-mediated endothelium-dependent vasodilatation. Methods Generally K_Ca can be divided into three types: Large-Conductance K_Ca,Intermediate-Conductance K_Ca and Small-Conductance K_Ca. According to different K_Ca blockers used in different groups,the rings were divided into the following groups: control group,Charybodotoxin(a blocker of BK_Ca and IK_Ca channels) group,Apamin(a specific blocker of SK_Ca channels) group,Charybodotoxin+Apamin group,Iberiotoxin(a specific blocker of BK_Ca channels) group. Rings from porcine coronary arteries were studied in the organ chamber,after equilibration for 1 hour,the control group rings were incubated with 7umol/L Indomethacin and 300 umol/L L-NNA,the other groups were incubated with 7umol/L Indomethacin,300 umol/L L-NNA and different calcium-activated potassium channel blockers. Then Pre-contraction tone induced by prostaglandin F2α U46619 and endothelium-dependent relaxation tone induced by bradykinin was measured in the presence of indomethacin and L-NNA with/without different calcium-activated potassium channel blockers. Results Compared with the control group,EDHF-mediated endothelium-dependent relaxation induced by bradykinin was significantly decreased in the Charybodotoxin group,Charybodotoxin+Apamin group and Iberiotoxin group,while the relaxation of Apamin group was not statistically significant in comparision with the control group. Conclusion Studies have shown that both BK_Ca and SK_Ca channels play a role in EDHF-mediated relaxation,and act in a coordinated manner on blood vessels,in addition,IK_Ca channel is also likely to play a role.