SummaryIntestinal absorption of Co58-labeled vit. B12 coenzyme (5,6-dimethylbenzimidazolyl cobamide) was studied in comparison with Co60-cyanocobalamin in rats. The results indicate that (a) quantitatively, absorption of orally administered coenzyme is about the same as that of cyanocobalamin. (b) Absorption of the coenzyme from the small intestine as determined by the “loop” technic is markedly enhanced by rat intrinsic factor and to the same extent as with cyanocobalamin. (c) There is no demonstrable preference in absorption between the 2 compounds when both are mixed and coadministered. (d) Slightly less of the absorbed radioactive coenzyme is flushed out in the urine by a large parenteral dose of unlabeled compound as compared with radioactive cyanocobalamin. These findings show that coenzyme behaves much like cyanocobalamin in intestinal absorption, quantitatively as well as in mechanism.
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Okuda et al. (1962) studied this question.