[Erythrocyte carbonic anhydrases in patients with hyperthyroidism (author's transl)]

Human erythrocyte carbonic anhydrase B (CA-B) and C (CA-C) were measured by a specific and immunological method and erythrocyte 2,3-diphosphoglycerate (2,3-DPG) concentrations were measured using a kinetical method. The levels of CA-B and CA-C were determined in normal subjects, patients with hyperthyroidism and patients with hypothyroidism, using the method of single radial immunodiffusion. A decrease of CA-B levels and an elevation of 2,3-DPG concentrations were noted in hyperthyroidism. The CA-C levels appeared to be essentially unchanged. Closely negative correlations were observed between CA-B levels and T3 resin sponge uptake T4, protein bound iodine levels, or 2,3-DPG concentrations. Simultaneously, the specific activity of CA-B and CA-C was determined using the immunoadsorbent method. The specific activity of CA-B elevated in hyperthyroidism two times higher than that of normal subjects. The levels of rabbit erythrocyte CA-B, CA-C and 2,3-DPG were measured in experimental hyperthyroidism by the methods employed for human erythrocytes. Thyroxin and 3,5,3'-triiodothyronine were administered orally for 30 days. A significant decrease in CA-B levels was observed after 30 days, although CA-C levels did not change significantly. These findings suggest that the steady state levels of CA-B is affected more readily than that of CA-C by thyroid hormone. An elevation of the specific activity of CA-B or the concentrations of 2,3-DPG was noted as seen in human hyperthyroidism. The effect of thyroid hormone on the biosynthesis of CA-B and CA-C was studied in vitro using rabbit reticulocyte lysates. The biosynthesis of CA-B was inhibited by the addition of thyroxin in this system, although no such an inhibitory effect was observed in the biosynthesis of CA-C. Th e clinical or pathological significances were discussed in relation to the changes in these isozymes and 2,3-DPG in red cells.