AJP - Gastrointestinal and Liver Physiology, Vol 256, Issue 1 158-G165, Copyright © 1989 by American Physiological Society
Dietary CHO and stimulation of carbohydrases along villus column of fasted rat jejunum
J. S. Morrill, L. K. Kwong, P. Sunshine, G. M. Briggs, R. O. Castillo and K. K. Tsuboi
Department of Pediatrics, Stanford University School of Medicine 94305.
Adult rats when fed a high carbohydrate diet of 70% sucrose or glucose for
24 h following a 4-day fast showed increased concentrations of intestinal
sucrase-isomaltase (EC 3.2.1.48, EC 3.2.1.10) and maltase-glucoamylase (EC
3.2.1.20) but not lactase-phlorizin hydrolase (EC 3.2.1.23, EC 3.2.1.62).
The concentration increases of these enzymes were accompanied by
corresponding acceleration of their synthesis rates. Contrary to earlier
studies by others, suggesting that upper villus cells in the fasted
intestine are unresponsive to stimulation of sucrase activity by refeeding
a high-sucrose diet, the concentration increases of both sucrase-isomaltase
and maltase-glucoamylase were seen to occur in cells all along the length
of the villus column. The earlier studies differed from the present study
by basing enzyme assays relative to protein rather than the DNA content of
villus cell fractions. We have shown that villus cells increase their
protein content severalfold while migrating to villus tip, providing the
basis for the difference between earlier and the present findings. Further
evidence that stimulation of sucrase-isomaltase and maltase-glucoamylase by
high carbohydrate is not restricted to the crypt and lower villus region
was obtained by the finding that their synthesis rates appeared to be
equally stimulated along the length of the villus column.
