Effects of vanadate and potassium depletion on renal H, K-ATPase protein expression

ABSTRACT

Background: Vanadate (V) inhibits while potassium (K) depletion stimulates collecting tubule H, K-ATPase activity. In the presence of V, K depletion could not restore the decreased H,K-ATPase activity. The effects of V and K depletion on renal H,K-ATPase protein expression might explain such observation.Objective: To examine the effects of V and K depletion on renal H,K-ATPase protein expression. Methods: Rats treated with normal saline solution (NSS) or V (5 mg/kg body weight) received either normal potassium (NK) or low potassium (LK) diet for 10 days. Protein expressions of renal H,K-ATPase \α₁ and \α₂ isoforms were determined by immunohistochemistry.Results: Both NK and LK animals treated with V had significantly increased vanadium levels in serum, urine, and renal tissues. LK diet caused hypokalemia. Animals treated with LK and V showed progressive hypokalemia. LK stimulated renal H,K-ATPase \α₁ protein expression in both cortex and medulla but enhanced H,K-ATPase \α₂ protein expression only in the cortex. Vanadate did not affect H,K-ATPase \α₁ protein expression in both NK and LK groups. Vanadate unaltered H,K-ATPase \α₂ protein expression in NK animals but could attenuate the increased expression in LK group.Conclusion: The magnitude of direct inhibitory effect of V on renal H,K-ATPase activity with small suppressive effect on protein expression is greater than the stimulatory effect of K depletion on H,K-ATPase activity and protein expression.