VANADATE CAUSES HYPOKALEMIC DISTAL RENAL TUBULAR-ACIDOSIS

Considerable evidence supports the presence of an H+-K+-ATPase along the mammalian nephron. Inhibition of this enzyme might be expected to reduce acid excretion while increasing potassium excretion, thus causing hypokalemic distal renal tubular acidosis (RTA). In this study we administered vanadate at a dose of 5 mg/kg ip for 10 days to rats. These animals developed hypokalemic distal RTA with a blood pH of 7.22 +/- 0.01, a plasma bicarbonate of 15.2 +/- 0.6 meq/l, and a plasma potassium of 3.28 +/- 0.06 meq/l. The vanadate-treated animals had a urine pH of 6.70 +/- 0.09, a value significantly higher than NH4Cl-treated animals with the same degree of acidemia (urine pH = 5.25 +/- 0.04). When cortical collecting tubules (CCT) from these animals were microdissected and H+-K+-ATPase was measured, it was decreased by approximately 75% (P < 0.001); but H+-ATPase was no different from control. In medullary collecting tubule, H+-K+-ATPase was also decreased but less than in CCT. Muscle potassium concentration in the vanadate-treated animals was significantly lower than in controls. These results demonstrate that vanadate causes hypokalemic distal RTA in association with inhibition of collecting tubule H+-K+-ATPase activity.