Intravenous injections of 1.5 µg. of 58Co B12 were given to subjects with normal serum B12 concentrations, to patients with vitamin B12 deficiency and to patients with chronic myelocytic leukemia.
The rate of plasma clearance of radioactivity after this dose was slowest in patients with chronic myelocytic leukemia and patients with pernicious anemia in severe relapse.
In patients with vitamin B12 deficiency, serum B12 concentrations were estimated microbiologically at frequent intervals after the injection. There was a good correlation between the results obtained by microbiological assay and as calculated from plasma radioactivity.
Significant differences were not observed between the urinary excretion of radioactivity by normal subjects and patients with B12 deficiency.