DISTRIBUTION OF LEUCYL NAPHTHYLAMIDASE AND ALKALINE PHOSPHATASE ON THE VILLI OF THE CHICK DUODENUM

Serial samples from successive levels of the villi and crypts were collected by sectioning a flattened piece of frozen duodenum parallel to the gut wall. Hatched chicks of 1 and 4 weeks of age were studied. Groups of sections were pooled for assay of enzyme activity and protein content. In both age groups, leucyl naphthylamidase was present in the crypts and highest at the bases of the villi while alkaline phosphatase (EC 3.1.3.1) was low or absent in the crypts and highest at the villi tips. Alkaline phosphatase at all levels of the villi hydrolyzed phenyl phosphate faster than β-glycerophosphate; the ratio of activities on these substrates was uniform along the length of the villi, but differed between age groups.