Abstract
The topographical distribution of alkaline phosphatase, acid phosphatase, and reduced diphosphopyridine nucleotide (DPNH) diaphorase in the small intestine of the normal rat, guinea pig, and rabbit has been studied by histochemical methods. Activity of these enzymes is pronounced in the mucosal epithelium. In the rat, alkaline and acid phosphatase are distributed along a gradient decreasing from duodenum to ileum, and in creasing from the neck of the crypts to the tip of the villi. In the guinea pig and the rabbit, maximal activity of both enzymes is observed in the middle third of the small intestine and at the base of the villi. DPNH diaphorase activity exhibits a gradient decreasing from the duodenum to the ileum in all three species examined. An incomplete survey indicates that monoamine oxidase (MAO) is also distributed along a gradient decreasing from duodenum to ileum in the guinea pig and rabbit; with the method used only traces of it have been demonstrated in the rat.