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Research Article Free access | 10.1172/JCI109548
Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115
Department of Medicine (Division of Gastroenterology), The Children's Hospital Medical Center, Boston, Massachusetts 02115
Find articles by Ulshen, M. in: JCI | PubMed | Google Scholar
Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115
Department of Medicine (Division of Gastroenterology), The Children's Hospital Medical Center, Boston, Massachusetts 02115
Find articles by Grand, R. in: JCI | PubMed | Google Scholar
Published October 1, 1979 - More info
To identify the site of stimulation of sucrase by a sucrose diet, changes in sucrase-specific activity of jejunal mucosa were studied after introduction of sucrose diet to carbohydrate-deprived rats. Results were correlated with simultaneous changes in villus gradients of sucrase-specific activity. Simultaneous with the introduction of sucrose diet, [3H]thymidine (100 μCi) was administered intravenously, and rates of cell migration measured during adaptation to the new diet. After a 72-h fast, rats fed sucrose diet for 6, 12, or 18 h showed no change in sucrase-specific activity in either whole mucosa or villus gradients. However, within 18-24 h after starting a sucrose diet, there was a marked rise in whole mucosal sucrase-specific activity above fasting values (99 ± 14 vs. 38 ± 4 μM glucose/min per g protein, P < 0.001) in association with the development of a region of increased activity at the lower villus (154 ± 22 vs. 60 ± 9 μM glucose/min per g protein, P < 0.02, but with no change in villus tip activity (56 ± 5 vs. 46 ± 8 μM glucose/min per g protein). Similar changes were seen in animals fed 24 h of sucrose diet after a 72-h carbohydratefree diet. Fasted animals fed sucrose diet for 36 h had increased sucrase-specific activity at the villus tip (144 ± 11 μM glucose/min per g protein) as well as at the lower villus region, and this pattern persisted at 1 wk of sucrose diet. Maximal activity patterns for isomaltase and maltase paralleled those for sucrase, but the villus gradients for lactase were unaffected by sucrose diet. The region of maximal sucrase-specific activity always coincided with or followed the leading edge of radioactivity as determined by liquid scintillation counting. Therefore, sucrose-mediated changes in sucrase activity of the jejunal mucosa in the rat appear to be initiated at the level of the crypt epithelial cell and are expressed after a latent period of 18-24 h during which these cells mature and migrate toward the villus tip.