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 t emperatures, 23 degrees C and 37 degrees C. In right ventricular myoca rdium, NIP-121 shortened the action-potential duration with little inf luence on other action-potential parameters at 37 degrees C, but not a t 23 degrees C. In whole-cell clamped ventricular myocytes, NIP-121 in duced a glibenclamide-sensitive outward current at 37 degrees C but no t at 23 degrees C. No difference in tissue adenosine triphosphate (ATP ) concentration was detected between ventricular myocardia incubated a t 37 degrees C and at 23 degrees C. In aortic preparations precontract ed with norepinephrine, NIP-121, cromakalim, and pinacidil produced en dothelium-independent relaxation at 37 degrees C, which was antagonize d by glibenclamide. The vasorelaxant effects were greatly reduced at 2 3 degrees C. Thus we demonstrated that the effects of K+ channel opene rs on the myocardium and vascular smooth muscle are temperature sensit ive.