Enhanced Absorption of Vitamin B 12 in Gastrectomized Rat by Rat Intrinsic Factor. ∗

Conclusions

1. The percentage excretion of radioactivity in the feces of normal and of totally gastrectomized rats, following administration of a single dose of 0.015 μg Co⁶⁰-B₁₂, was determined by scintillation counting. 2. The gastrectomized rats apparently were unable to absorb the labelled vit. B₁₂ (100% fecal excretion). 3. Simultaneous administration of homogenized rat stomach or of rat gastric juice but not of human gastric juice or of an extract of hog stomach mucosa reproduced in the gastrectomized rat the capacity of the normal rat to absorb the test dose of Co⁶⁰-B₁₂ administered (60% fecal excretion). 4. The rat, like man, secretes intrinsic factor largely, if not exclusively, into the stomach; but sources of human and hog intrinsic factor possess little or no activity in the rat. 5. The observations of Watson and Florey indicate that in the rat the secretion of intrinsic factor is probably confined to the distal secretory portion of the stomach.