Control by drugs of renal potassium handling.

This review has focused on the influence of several diuretic drugs on potassium handling by the kidney. One class of drugs (loop diuretics) acts by directly inhibiting a potassium absorptive mechanism in the luminal membrane of cells of the thick ascending limb of Henle's loop. Two other groups of diuretics affect potassium transport indirectly by inhibiting salt and water absorption upstream from the potassium secretory site in the late distal tubule: carbonic anhydrase inhibitors act in the proximal tubule; thiazides act in the early distal tubule. The subsequent increase in lumen flow rate then stimulates net potassium secretion by the distal tubule. A fourth class of drugs (spironolactone) acts by antagonizing the response of the distal tubule to aldosterone. These drugs decrease the ability of aldosterone to stimulate distal potassium secretion. Finally, a fifth group of drugs (potassium-sparing diuretics) decreases potassium secretion by increasing the luminal membrane voltage and thus decreasing the electrochemical gradient for potassium exit from the cell.