Studies on Poisonous Metals. IV. Absorption of Stannic Chloride from Rat Alimentary Tract and Effect of Various Food Components on Its Absorption

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Abstract
In order to examine the characteristics of intestinal absorption of stannic chloride, an in vitro experiment was carried out by circulating the reagent through segments of everted rat small intestine. The disappearance of tin from the mucosal solutions of rat duodenum, jejunum, and ileum followed apparent first-order kinetics. Tin absorption was approximately proportional to the concentration of tin in the mucosal solution and no difference was observed in the absorptions by rat duodenum, jejunum, and ileum. These results suggested that the absorption of tin from the rat small intestine occurs by passive diffusion. The effect of various food components such as organic acids, amino acids, and proteins on tin absorption from the rat intenstine and on its uptake by the intestine was also studied by the use of the small intestine in vitro and in vivo. Organic acids such as citric acid, tartaric acid, malic acid, and ascorbic acid significantly enhanced the tin absorption in vitro and in vivo. Tin uptake greatly decreased in the presence of these acids. Amino acids such as L-histidine, L-proline, and L-glutamic acid, and proteins such as ovalbumin and gelatin had little effect on tin absorption in vitro and in vivo. In addition, it was suggested that the effect of citric acid on the intestinal absorption of tin was due to a modification of intestinal permeability and the enhanced permeation of tin across the intestine in the form of tin-citric acid complex.