THE IN VITRO BINDING OF COBALT60 LABELED VITAMIN B1 BY NORMAL AND LEUKEMIC SERA

Abstract

In normal subjects, the average serum vitamin B12 concentration was 0.64 mug/ml; the vitamin B binding capacity of the serum (UBBC) was 1.51 m[mu]g/ml; and the total vitamin B12 binding capacity (TBBC) 2.23 m[mu]g/ml. Myelogenous leukemia patients had an average serum concentration of 8.09 m[mu]g/ml; a UBBC of 8.87 m[mu]g/ml; and a TBBC of 16.86 m[mu]g/ml. Following treatment, the UBBC fell rapidly to normal, while the decline in serum vitamin B12 concentration was more gradual. Two patients with chronic monocytic leukemia, and one with leukocytosis had an increase in serum vitamin B12 concentration and UBBC. Six of 8 patients with leukocytosis and 1 of 3 with acute leukemia had normal serum vitamin B12 levels but elevated UBBC''s. Patients with chronic lymphocytic leukemia had a concentration of vitamin B12 and UBBC within normal range. The beta globulins bound an average of 44% of the added Co60 vitamin B12 (average 0.79 m[mu]g/ml) and was the chief binding protein in 16 of 18 normal subjects. The alpha-2-globulin was next in binding ability (an average of 28% and 0.59 m[mu]g/ml). The alpha-1 globulins bound the least Co60 vitamin B12 of any of the 5 protein fractions. The alpha-1 globulins were the chief binding protein of 5 of 10 patients with chronic myelogenous leukemia, binding an average of 38% of the added Co60 vitamin B12 (3.55 m[mu]g/ml). The alpha-2 globulins were the chief binding protein in 4 of the 10 patients, binding an average of 34% (3.07 m[mu]g/ml). With treatment of the disease, the pattern of vitamin .B12 binding by the serum proteins returned towards normal. An increase in the binding of Co60 vitamin B12 by the alpha-1 and alpha-2 globulins was noted in 1 patient with chronic monocytic leukemia, and 1 with leukocytosis. Four other patients with elevated UBBC''s of varying degree, due to diseases other than chronic myelogenous leukemia, had an increase in vitamin B12 by the alpha-2 globulins but no increase in alpha-1 globulin binding. In addition to an increased serum concentration of, and binding capacity for vitamin B12 in chronic myelogenous leukemia, there is an abnormal distribution of added vitamin B12 among the serum protein fractions in this disease.