Red‐Cell Carbonic Anhydrase Isoenzymes in Megaloblastic Anaemia

Erythrocyte carbonic anhydrase isoenzymes B and C have been measured by means of electrophoresis on cellulose acetate membrane strips followed by staining, elution and spectrophotometry. The results from 30 normal subjects showed for carbonic anhydrase B a mean and standard deviation of 12.1 ± 1.4 mg/g Hb, and for carbonic anhydrase C, 3.9 ± 0.9 mg/g Hb. Both isoenzymes were markedly increased in all 10 cases of untreated megaloblastic anaemia, the mean ± SD for carbonic anhydrase B being 24.8 ± 7.6 mglg Hb and for the isoenzyme C, 7.7±k 1.2 mg/g Hb. These results are both highly significantly greater than the normal means (P < 0.001). The elevated levels of both isoenzymes returned to the normal range within 2–4 weeks of starting vitamin B12 therapy in 3 patients with pernicious anaemia in whom serial enzyme measurements were made. In a group of 13 patients with pernicious anaemia, who had been adequately treated with vitamin BIZ for 1–15 years, the mean levels of isoenzymes B and C were 10.3 ± 0.6 and 2.9 ± 0.7 mg/g Hb respectively; both these mean results are significantly less than the corresponding normal means (P < 0.001).