Regional differences in transport, lipid composition, and fluidity of apical membranes of small intestine of chicken.
Na+-dependent D-glucose transport was studied in brush-border membrane vesicles from duodenum, jejunum, and ileum of 5- to 6-wk-old chickens. Regional differences were found, and both initial rates and accumulation ratio of D-glucose were higher in the proximal part of the small intestine than in the ileum. To establish the mechanism(s) underlying these differences we have studied the density of Na+-dependent D-glucose cotransporter (SGLT1) as well as lipid composition and fluidity. Phlorizin-specific binding and Western blot analysis indicated a decrease in the amount of SGLT1 in the ileum when compared to the duodenum and jejunum. The distal part of the small intestine also showed a decrease in free cholesterol content and saturated-to-unsaturated fatty acid ratio together with an increase in lipid content and phosphatidylcholine-to-sphingomyelin ratio. These results were associated with a decrease in the diphenylhextriene fluorescence polarization found in brush-border membranes of the ileum. We can conclude that the decrease in the apical D-glucose transport found in the ileum is primarily due to a reduction in the amount of SGLT1 present in the brush-border membrane rather than the differences in the lipid composition and fluidity.
Garriga
C
C
Department de Fisiologia-Divisió IV, Facultat de Farmàcia, Universitat de Barcelona, Spain.
Vázquez
C M
CM
Ruiz-Gutiérrez
V
V
Planas
J M
JM
D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western / Q000662:veterinary; D002645:Chickens / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis; D005454:Fluorescence Polarization / Q000662:veterinary; D005947:Glucose / Q000378:metabolism; D007421:Intestine, Small / Q000737:chemistry*; D008297:Male; D008560:Membrane Fluidity / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000032:analysis*; D008563:Membrane Lipids / Q000032:analysis*; D008871:Microvilli / Q000737:chemistry / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000032:analysis*; D010695:Phlorhizin / Q000378:metabolism; D010743:Phospholipids / Q000032:analysis; D051269:Sodium-Glucose Transporter 1
D005227:Fatty Acids; D008562:Membrane Glycoproteins; D008563:Membrane Lipids; D009004:Monosaccharide Transport Proteins; D010743:Phospholipids; D051269:Sodium-Glucose Transporter 1; D010695:Phlorhizin; D005947:Glucose