Effect of diet on glucose transporter site density along the intestinal crypt-villus axis.
High-carbohydrate diets stimulate intestinal brush-border glucose uptake and increase the number of glucose-protectable phlorizin binding sites, but it has been unknown where along the crypt-villus axis these effects are expressed. We attacked this problem by three methods. First, by measuring phlorizin binding to isolated mouse enterocytes fractionated along the crypt-villus axis by the Weiser method, we identified a high-affinity binding site predominating from villus tip to midvillus and a site of possibly lower affinity predominating in the crypts. A high-carbohydrate diet increased by severalfold the density of the villus sites and probably also of the crypt sites, without changing their binding constants. Second, autoradiography revealed increased glucose-protectable phlorizin binding along the whole crypt-villus axis on a high-carbohydrate diet. Finally, a polyclonal antibody against the Na(+)-glucose cotransporter recognized a protein in the brush-border membrane of villus cells. Hence, substrate-dependent upregulation of intestinal glucose transport involves increased numbers of transporters along the crypt-villus axis.
Ferraris
R P
RP
Department of Physiology, University of California Medical School, Los Angeles 90024-1751.
Villenas
S A
SA
Hirayama
B A
BA
Diamond
J
J
D000704:Analysis of Variance; D000818:Animals; D001345:Autoradiography; D002478:Cells, Cultured; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D007583:Jejunum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051379:Mice; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D010695:Phlorhizin / Q000378:metabolism; D012016:Reference Values; D012044:Regression Analysis; D014316:Tritium
D004040:Dietary Carbohydrates; D009004:Monosaccharide Transport Proteins; D014316:Tritium; D010695:Phlorhizin