Potassium Deficiency and Cardiac Catecholamine Metabolism in the Rat

Norepinephrine metabolism, arterial blood pressure, and electrolytes were studied in rats maintained on either potassium-deficient or control diets. After 3 weeks on the test diets, the arterial blood pressure was significantly lower and the ratio of [Na] to [K] in cardiac tissue was significantly higher in potassium-deficient rats as compared to controls. Ten minutes after intravenous injection of 3 H-norepinephrine the specific activity of cardiac norepinephrine was similar in the control and potassium-deficient groups despite a significant increase in endogenous norepinephrine concentration in the potassium-deficient hearts. But 24 hours after injection, there was a significant increase in 3 H-norepinephrine specific activity, concentration, and content in the potassium-deficient group. Cardiac tissue monoamine oxidase activity was similar in both groups. The increased 3 H-norepinephrine retention and concentration and the decreased arterial blood pressure of the potassium-deficient rate suggest an impairment in norepinephrine release by the sympathetic neurons.