Inactive form of carbonic anhydrase I in erythrocytes from primary aldosteronism

An inactive form of erythrocyte CA I was found in patients with primary aldosteronism. The levels of CA I in the patients were within the normal range: however, the specific esterase activity of CA I from three patients was in the range of 0.12-0.26 u/mg CA I (normal control: 0.66 +/- 0.1 u/mg CA I). In one subject, who had been treated with spironolactone, the specific activity of CA I was in the normal range. However after the termination of the drug the specific activity of CA I decreased to 0.3 u/mg CA I. Two months after adrenalectomy, the specific activity of the subjects was restored. The inactive CA I isolated from a patient was not immunologically distinguishable from that of normal individuals. The level of zinc in the inactive CA I was not different from that of normal CA I. The inhibitory effect of acetazolamide on the inactive CA I was weaker than that on normal CA I. The binding affinity of 3[H]acetazolamide to the inactive CA I was also lower than that of normal CA I. These results suggested the presence of a novel variant form of CA I in this disease.