Effects of phloretin and theophylline on 3-O-methylglucose transport by intestinal epithelial cells
- 1 March 1978
- journal article
- research article
- Published by American Physiological Society in American Journal of Physiology-Cell Physiology
- Vol. 234 (3), C64-C72
- https://doi.org/10.1152/ajpcell.1978.234.3.c64
Abstract
Phloretin and theophylline each exert an immediate inhibitory effect on the Na+-independent, facilitated-diffusion transport system for sugar associated with intestinal epithelial cells. Phloretin inhibits approximately 50% more of the total Na+-independent sugar flux than theophylline. Neither agent has an immediate effect on the Na+-dependent, concentrative sugar transport system, although preincubation of the cells with phloretin causes a significant inhibition. The slowly developing effect is correlated with a decrease in cellular adenosine triphosphate (ATP) and an elevation of intracellular Na+. Other agents which elevate cell Na+ also inhibit Na+-dependent sugar influx, even if ATP levels are not depleted. On the other hand, if ATP is depleted by phloretin under conditions in which the cells do not gain Na+, the inhibitory effect on Na+-dependent sugar flux tends to disappear. The slow-onset phloretin effects are due to transinhibition of the Na+-dependent sugar carrier by cellular Na+. When the passive sugar carrier is inhibited by phloretin or theophylline, the concentrative system can establish an enhanced sugar gradient. Because of the secondary metabolic effects of phloretin, theophylline induces a greater gradient enhancement despite its more limited effect on the passive sugar-transport system. Sugar gradients as large as 20-fold are induced by theophylline, in contrast to 12-fold gradients observed in the presence of phloretin and approximately 7- to 8-fold for untreated cells. These results are discussed in terms of conceptual questions regarding the energetics of Na+-dependent transport systems.This publication has 33 references indexed in Scilit:
- 2-Deoxyglucose transport by intestinal epithelial cells isolated from the chickThe Journal of Membrane Biology, 1976
- Differences in neutral amino acid and glucose transport between brush border and basolateral plasma membrane of intestinal epithelial cellsJournal of Cellular Physiology, 1976
- A Na+-independent, phloretin-sensitive monosaccharide transport system in isolated intestinal epithelial cellsThe Journal of Membrane Biology, 1975
- d-Galactose accumulation in rabbit ileum effects of theophylline on serosal permeabilityBiochimica et Biophysica Acta (BBA) - Biomembranes, 1975
- The sequestration of Na+, K+ and Cl− in the cellular nucleus and its energetic consequences for the gradient hypothesis of amino acid transport in Ehrlich cellsBiochimica et Biophysica Acta (BBA) - Biomembranes, 1974
- Effect of K+ and K+ gradients on accumulation of sugars by isolated intestinal epithelial cellsThe Journal of Membrane Biology, 1973
- Effects of inhibitors on 3-O-methylglycose transport in rabbit ileumThe Journal of Membrane Biology, 1972
- An example of mutual competition between transport inhibitors of different kinetic type: The inhibition of intestinal transport of glucalogues by phloretin and phlorizinBiochimica et Biophysica Acta (BBA) - Biomembranes, 1972
- Active sugar accumulation by isolated intestinal epithelial cells. A new model for sodium-dependent metabolite transportBiochemistry, 1970
- Sodium and Sugar Fluxes across the Mucosal Border of Rabbit IleumThe Journal of general physiology, 1969