Potassium and sodium excretion and potassium homeostasis during acute hypokalemia

¹ Department of Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York

Decreased potassium and increased sodium excretion were observed in dogs acutely potassium-depleted by hemodialysis. Potassium excretion at constant blood pH varied directly with plasma [K⁺]. When filtered Na load and urine flow were constant during K⁺ depletion, increase in Na excretion was equivalent to decrease in K⁺ excretion, suggesting close coupling between transtubular movements of the two ions. Large changes in plasma [K⁺] (30%) and K⁺ excretion (50%) were produced with removal of a relatively small amount (estimated 3%) of total body K⁺. Plasma [K⁺] decrease during depletion was rapidly decelerated by movement of intracellular K⁺ into the extracellular fluid (ECF). When ECF [K⁺] stabilized, further decrease in K⁺ excretion ceased despite continued reduction of total body K⁺. It appears: 1) that tubular secretion of K⁺ is directly and rapidly responsive to reduction in ECF [K⁺]; 2) that low ECF [K⁺] may simultaneously impair contraluminal K⁺ uptake and Na extrusion, reducing K⁺ excretion and Na reabsorption during acute hypokalemia. Stoichiometry of changes suggests a 1:1 coupling between K⁺ secretion and moiety of Na reabsorption in the distal nephron.

Key Words: hypokalemia, acute, effects on K⁺ excretion • hypokalemia, acute, effects on Na excretion • hypokalemia, acute, effects on NH₃ excretion • hypokalemia, acute, effects on H • excretion • potassium excretion, effect of acute hypokalemia • potassium excretion, relation to plasma K⁺ • potassium excretion, relation to Na excretion • potassium, homeostasis of plasma [K⁺] • sodium excretion, effect of acute • hypokalemia

Submitted on October 19, 1964