STUDIES ON THE ABSORPTION OF VITAMIN B12

Abstract

For the purpose of investigating whether or not Co60-B12 absorption tests are successfully applicable to Japanese subjects, the intestinal absorption of orally administered Co60-B12 was studied for the first time on the Japanese patients suffering from hematologic disorders including Addisonian pernicious anemia as well as the normals. At the same time, in view of the fact that pernicious anemia is rare in Japan, an attempt was made to study the difference in B12 metabolism between the Japanese and the European or the American pernicious anemia patients. As the methods for measuring intestinal absorption of B12, fecal or urinary excretion tests and hepatic uptake method were used in this study. Prior to this study, some fundamental investigations were made on these methods. The results obtained are as follows:1. In Japanese normals, fecal excretion was 29.0±9.0% of the radioactivity of the oral Co60-B12 on the average, urinary excretion 17.4±6.8%, and hepatic uptake 8.74±2.93%, showing a good agreement with those in the foreign normals.2. The measurement of hepatic uptake presented the evidence that absorbed B12 was preferentially taken up by the liver in the Japanese as well. It was also found that 0.2 or 0.5μg of Co60-B12 should be given as a test dose in urinary excretion test, since percentage urinary radioactivity was significantly decreased when the oral dose was raised above 1.0μg.3. In hematologic disorders such as leukemia, aplastic anemia, iron deficiency anemia, hemolytic anemia, lupus erythematosus, or anemia due to the lodging of tape worm, there could be observed no significant defect in B12 absorption.4. However, in three cases of pernicious anemia in relapse or in remission, B12 absorption was exceedingly abolished without exception, unless hog intrinsic factor concentrate was added. This fact indicates that the pathogenesis of pernicious anemia of the Japanese patients was quite identical with the patients of other countries.5. In addition, a diagnostic availability of B12 absorption tests for the differentiation of pernicious anemia from other resembling megaloblastic anemias was also referred to.Thus, the author was led to the general conclusion that B12 absorption test was also well applicable to Japanese subjects and that the mechanism of pernicious anemia was identical with each other, irrespective of the patients' nationality, no matter how low the incidence of pernicious anemia may be.