Temperature-sensitive effects of potassium channel openers on isolated guinea pig myocardium and aorta

The effects of K+ channel openers, NIP-121, cromakalim, and pinacidil, on isolated myocardium and aorta were investigated at two different temperatures, 23 degrees C and 37 degrees C. In right ventricular myocardium, NIP-121 shortened the action-potential duration with little influence on other action-potential parameters at 37 degrees C, but not at 23 degrees C. In whole-cell clamped ventricular myocytes, NIP-121 induced a glibenclamide-sensitive outward current at 37 degrees C but not at 23 degrees C. No difference in tissue adenosine triphosphate (ATP) concentration was detected between ventricular myocardia incubated at 37 degrees C and at 23 degrees C. In aortic preparations precontracted with norepinephrine, NIP-121, cromakalim, and pinacidil produced endothelium-independent relaxation at 37 degrees C, which was antagonized by glibenclamide. The vasorelaxant effects were greatly reduced at 23 degrees C. Thus we demonstrated that the effects of K+ channel openers on the myocardium and vascular smooth muscle are temperature sensitive.