Effect of Hypercapnia on Myocardial Potassium Movement in the Dog

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Abstract
This investigation tested the hypothesis that uptake of potassium during respiratory acidosis is secondary to the increased catecholamine activity which accompanies hypercapnia. The plasma K+ concentration of simultaneously drawn arterial and coronary sinus blood samples from dogs was determined under three conditions: (1) hypercapnia (25% CO2-75% O2), (2) normocapnia (25% N2-75% O2) + propranolol (a beta-receptor blocker), and (3) hypercapnia + propranolol. The change during hypercapnia from uptake of K+ to loss of K+ after administration of propranolol (0.05 mg/kg, iv) was statistically significant. However, the administration of propranolol during normocapnia had no effect on myocardial K+ movement. Changes in heart rate and myocardial contractility did not explain the change in myocardial K+ movement during hypercapnia following the administration of propranolol. These data suggest that uptake of K+ is secondary to the increased catecholamine activity which accompanies hypercapnia.