Abstract
Segments of the gastrointestinal tract removed from rats after intervals of time following injection of S35-sulfate were fixed in aqueous formalin and then washed in water. Coated autoradiograms revealed that 6 hours after administration more of the S35 was present in the goblet cells lying deep in the crypts of the mucosa than in those adjacent to the intestinal lumen. By the 24th hour the concentration of the radioisotope was strikingly higher and more uniform from cell to cell and the mucus in the intestinal lumen was highly radioactive. At the end of 48 hours very little of the S35 remained in the intestinal wall or could be made out in the mucus of the lumen; the autoradiographic reaction was faint and diffuse as contrasted with the punctiform and intense reaction given by the specimens removed at the end of shorter intervals of time.