K V 7 channels are involved in hypoxia‐induced vasodilatation of porcine coronary arteries

Background and Purpose Hypoxia causes vasodilatation of coronary arteries, but the underlying mechanisms are poorly understood. We hypothesized that hypoxia reduces intracellular Ca 2+ concentration ([ Ca 2+ ] i ) by opening of K channels and release of H 2 S . Experimental Approach Porcine coronary arteries without endothelium were mounted for measurement of isometric tension and [ Ca 2+ ] i , and the expression of voltage‐gated K channels K V 7 channels (encoded by KCNQ genes) and large‐conductance calcium‐activated K channels ( K Ca 1.1) was examined. Voltage clamp assessed the role of K V 7 channels in hypoxia. Key Results Gradual reduction of oxygen concentration from 95 to 1% dilated the precontracted coronary arteries and this was associated with reduced [ Ca 2+ ] i in PGF 2α (10 μM)‐contracted arteries whereas no fall in [ Ca 2+ ] i was observed in 30 mM K ‐contracted arteries. Blockers of ATP ‐sensitive voltage‐gated potassium channels and K Ca 1.1 inhibited hypoxia‐induced dilatation in PGF 2α ‐contracted arteries; this inhibition was more marked in the presence of the K v 7 channel blockers, XE991 and linopirdine, while a K V 7.1 blocker, failed to change hypoxic vasodilatation. XE991 also inhibited H 2 S ‐ and adenosine‐induced vasodilatation. PCR revealed the expression of K V 7.1 , K V 7.4 , K V 7.5 and K Ca 1.1 channels, and K Ca 1.1, K V 7.4 and K V 7.5 were also identified by immunoblotting. Voltage clamp studies showed the XE991 ‐sensitive current was more marked in hypoxic conditions. Conclusion The K V 7.4 and K V 7.5 channels, which we identified in the coronary arteries, appear to have a major role in hypoxia‐induced vasodilatation. The voltage clamp results further support the involvement of K V 7 channels in this vasodilatation. Activation of these K V 7 channels may be induced by H 2 S and adenosine.