The absorption of vitamin B12 in normal and gastrectomized rats and the effect of some gastric extracts

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Abstract
Absorption of radioactive vitamin B12 was measured in normal and gastrectomized rats by estimation of fecal radioactivity. In normal rats, the percent vitamin absorbed per vitamin ingested decreased markedly at higher dose levels (over 100 mug) while at very low levels (5 mug) there was no absorption. Gastrectomized rats showed greatly reduced absorption from normal rats when a constant dose level was given (5.5% as compared to 42.9% in normal rats). Administration of rat gastric juice raised absorption of the vitamin to 15.9% in gastrectomized rats, but had no effect on normal rats. Further evidence of existence of a rat intrinsic factor was given by increased vitamin B12 absorption in presence of rat stomach extract in a tied-off intestinal loop in an otherwise intact rat. Human gastric juice depressed vitamin B12 absorption in normal rats to 25.4% and in gastrectomized rats to 1.5%, suggesting a species specificity of intrinsic factor.