The physiological significance of Co^<58>-labeled 5,6-dimethylbenzimidazolyl cobamide coenzyme has been studied in terms of its absorption, tissue distribution and binding with human gastric juice. Schilling's urinary excretion test of coenzyme B_<12> gave the results of 1.6-2.6% in mormal human subjects and 0.2-0.6%, which were enhanced by hog intrinsic factor preparation, in patients with pernicious anemia in remission who showed the abolishment of vitamin B_<12> absorption. Coenzyme B_<12> was taken up preferentially by the liver and kidneys in Wistar strain rats, following either oral or intravenous administration. Human gastric juice binds with coenzyme B_<12> and makes it nondialyzable. Coenzyme B_<12> binders in the paper-electrophoregram of gastric juice revealed the same pattern as vitamin B_<12> binders.
