Involvement of multiple sodium ions in intestinal d-glucose transport.
Brush border membrane vesicles isolated from rabbit small intestine were used to measure the interactions between sodium and glucose transport with a rapid uptake technique. A plot of glucose uptake rate vs. increasing sodium concentration yielded a sigmoid curve. Hill analysis revealed a coefficient of 1.9 +/- 0.02 (+/- SEM), consistent with at least two sodium ions involved in glucose transport. Transport coupling was then measured directly with double-label experiments in which the uptakes of D-glucose and sodium were determined in the presence and absence of cotransported solute. At the earliest time point, the ratio of cosubstrate-dependent sodium transport to glucose transport was 3.2 +2- 0.7 (+/- SEM). We conclude that two or more sodium ions are coupled to glucose transport across the intestinal brush border membranes.
D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000378:metabolism; D007700:Kinetics; D008433:Mathematics; D008871:Microvilli / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*
D012964:Sodium; D005947:Glucose