Red blood cell carbonic anhydrase activity in children with distal renal tubular acidosis.

Red blood cell carbonic anhydrase activity was studied in three children with distal renal tubular acidosis, the parents of one of the patients, and in control subjects. Although each patient had distal renal tubular acidosis as defined by an inappropriately high urine pH in the face of a systemic metabolic acidosis, hyperchloremia and a low (U-B)pCO2, they differed in that two had deafness. The deafness was inherited as an autosomal recessive mode in one and by an autosomal dominant gene in the other. Red blood cell carbonic anhydrase activity was determined in hemoglobin-free hemolysate by the esterolytic action of the enzyme on the substrate p-nitrophenyl acetate. The two isoenzymes, B and C, of carbonic anhydrase were identified using polyacrylamide disc gel electrophoresis. The red blood cell carbonic anhydrase activity of nine control children aged 2-10 years was 3.8 (3.2-5.0) units/g Hb. The values obtained from the three patients were 3.0, 3.7, and 4.36 units/g Hb. These did not differ from those of the control subjects. No abnormalities were found in the ratios of the B and C peaks or in their electrophoretic mobility.