Enhanced Absorption of Vitamin B12 in Gastrectomized Rat by Rat Intrinsic Factor.

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Abstract
The percentage excretion of radioactivity in the feces of normal and of totally gastrectomized rats for 4 days following the administration of a single dose of 0.015 [mu]g Co60_B12 was determined by scintillation counting. The vitamin B12 given had a specific activity of about 1 [mu]c/[mu]g. Eleven observations were made on as many normal rats and over 60 observations were made on 14 gastrectomized rats which remained in apparent good health on a synthetic nutritionally complete low-residue diet containing 18% casein. The gastrectomized rats apparently were unable to absorb the labeled vitamin B12 (100% fecal excretion of radioactivity). Simultaneous administration of 1/2 of a homogenized rat stomach or of 3 ml of rat gastric juice but not of 2 or 6 ml of human gastric juice or of 4 or 20 mg 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 of radioactivity). It is concluded that the rat, like man, secretes intrinsic factor largely, if not exclusively, in the stomach but that clinically active sources of human and of hog intrinsic factor possess little or no activity in the rat perhaps because of species specificity. The utility of the totally gastrectomized rat in permitting observations on the pathologic physiology of vitamin B12 assimilation seems clear.