Vitamin B12 absorption in x-irradiated rats.

The effect of whole-body exposure of rats to a sub-lethal dose (400 rad) of x-rays on the absorptive capacity of intestinal mucosal cells for vitamin B12 has been studied. The rate of absorption of vitamin B12 from the intestinal loops is decreased in x-irradiated rat. Inclusion of gastric juice from normal rat does not improve the rate. A severe interference in the absorption and retention of orally fed (57-Co)-B12, as evidenced by low serum levels, decreased organ uptake and increased excretion, is observed. However, when the vitamin is administered intraperitoneally, its uptake by organs is not affected in the irradiated animal. This suggests that the observed morphological degeneration of mucosal cells in x-irradiated rats is the main reason for the malabsorption of vitamin B12. Atrophy of intestinal cells in the protein-fasted rat accentuates the adverse effects of radiation. A sharp drop in viable intestinal flora is observed within 24 h post-irradiation, but there is an increase after 3 days.