DISTRIBUTION AND REGULATION OF ORNITHINE DECARBOXYLASE ACTIVITY ALONGTHE VILLUS-CRYPT AXIS IN THE SMALL-INTESTINE

Distribution of ornithine decarboxylase activity in rat intestinal vil li and crypts was determined by serially sectioning frozen mucosa and measuring enzyme activity in pools of sections composed of villi or cr ypts. Contents of the pools was determined by histological examination of representative sections, and simultaneous measurement of sucrase a s a marker of villus samples demonstrated excellent separation of vill i and crypts. In fasted and ad lib fed rats, enzyme activity was highe st in the villus-crypt junctional area and in crypts (P < 0.05). Refee ding after a fast increased enzyme activity 15-fold, with greatest act ivity in villus tips and the villus-crypt junctional area. Luminal 0.4 M glycine stimulated enzyme activity only in villus and villus-crypt junctional samples, while luminal 10 mM putrescine stimulated activity only in crypts. Parenteral epidermal growth factor caused increased e nzyme activity in all mucosal areas, but the 18-28-fold increase in th e three villus samples (top, middle and bottom) was significantly grea ter(P < 0.05) than the 7-9-fold increase in crypt and junctional sampl es. In rats refed after a fast, parenteral putrescine (2 mmol/kg) depr essed enzyme activity in all mucosal areas. Ornithine decarboxylase ac tivity is usually greatest in junctional and crypt cells, and villus a nd crypt cells respond differently to luminal and systemic stimuli.