Absence of H⁺-ATPase in cortical collecting tubules of a patient with Sjogren's syndrome and distal renal tubular acidosis

Distal urinary acidification abnormalities may arise from transepithelial voltage defects, permeability defects, or proton-secretory defects, but tests to determine the cellular mechanisms underlying secretory abnormalities have not previously been reported. A patient with Sjogren's syndrome and distal renal tubular acidosis due to a secretory defect is described, whose kidney biopsy was examined by fluorescent immunocytochemistry with an antibody to the M_r 31,000 subunit of the mammalian kidney vacuolar H⁺-ATPase and was compared with normal human kidney. Staining with the anti-H⁺-ATPase antibody in normal human kidney was detected in the brush border microvilli and subvillar invaginations of the proximal tubule and in intercalated cells in the collecting duct. A biopsy sample from the patient was devoid of any anti-H⁺-ATPase staining in the intercalated cells. Staining was also absent from the proximal tubule brush border microvilli but was present in the subvillar invaginations. Although autoantibodies to normal human kidney membrane proteins were detected in the serum by immunoblot analysis, no immunocytochemical evidence for anti-intercalated cell autoantibodies was observed in the patient's serum. This report demonstrates that the basis for the proton secretory defect in some patients with distal renal tubular acidosis is likely the absence of H⁺-ATPase in the intercalated cells. It also illustrates the potential diagnostic utility of anti-H⁺-ATPase antibodies in the classification of distal renal tubular acidoses.