Effect of transmembrane pH gradient changes on potassium-induced relaxation in vascular smooth muscle.
In bicarbonate-buffered solution the Ba++-induced contraction of rat aorta was relaxed by an elevated extracellular K+ concentration. When the pH of the bicarbonate-buffered solution was lowered or the buffer system of the solution changed from bicarbonate to Tris or HEPES, the K+-induced relaxation was strongly inhibited. Raising the pH of the Tris-buffered solution restored the effect of K+. Addition of NH4+, which is known to cause a transient increase in intracellular pH, transiently inhibited and subsequently augmented the K+-induced vasodilation in all solutions. It is suggested that the K+-induced vasodilation results from membrane hyperpolarization following enhanced Na+, K+-ATPase activity and that this K+-induced vasodilation is affected by changes in the transmembrane pH gradient.
D000818:Animals; D002021:Buffers; D006863:Hydrogen-Ion Concentration; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000494:pharmacology*; D051381:Rats
D002021:Buffers; D011188:Potassium