The effect of diuretics on lymphocyte magnesium and potassium.

Lymphocytes have advantages over other tissues, such as erythrocytes and muscle, for assessing intracellular magnesium and potassium. During experimental magnesium deficiency in rats, the magnitude of the magnesium loss from lymphocytes was similar to that of cardiac and skeletal muscle. During experimental potassium deficiency, cardiac muscle retained potassium more effectively than skeletal muscle. The magnitude of the potassium loss from lymphocytes was of similar magnitude to that of cardiac muscle. Chronic congestive heart failure patients being treated with the loop-blocking diuretic, furosemide, were found to have significantly reduced lymphocyte magnesium (p less than 0.05) and potassium (p less than 0.01) compared to values obtained in 20 control subjects. The effects of acute administration of the potassium-sparing diuretic, amiloride, were investigated in 10 congestive heart failure patients. Each patient was studied over a 6-day period comprising a 3-day control period involving furosemide administration, followed immediately by a 3-day test period when amiloride (10 mg twice daily) was added to the therapeutic regimen. Amiloride reduced urinary potassium and magnesium, and increased both plasma and lymphocyte potassium and magnesium. Under these conditions, amiloride exerted magnesium-sparing actions in addition to its well-established potassium-sparing actions. The magnesium-sparing actions may be beneficial in that many experimental studies have shown that magnesium is required for maintenance and restoration of cell potassium.