Studies on potassium induced coronary dilation in the isolated guinea pig heart

Changes of coronary flow in the isolated perfused spontaneously beating guinea pig heart were induced by elevation of potassium concentration in the perfusion medium (4-16 meq/l). Potassium caused a dose-dependent transient increase of diastolic coronary inflow. The response was inhibited by ouabain (1.4 X 10(-7) M) or reduced temperature. Rubidium ions elicited almost identical vasodilator effects which were also inhibited by ouabain. Autoregulation of coronary flow, reactive hyperemia, and hypoxic coronary dilation were not significantly altered in the presence of ouabain. The results support the hypothesis that potassium as well as rubidium cause vasodilation by activating a Na+, K+-ATPase. On the other hand, they do not favour the view of an essential involvement of potassium ions in local regulation of coronary flow under the conditions studied.