Evidence for an intestinal Na+:sugar transport coupling stoichiometry of 2.0.
Membrane potentials maintained by normally-energized intestinal epithelium interfere with an accurate determination of the Na+:sugar coupling stoichiometry associated with Na+-dependent transport systems. The interference is due to the fact that basal Na+ influx is itself a potential-dependent event, and sugar transport induces a membrane depolarization which therefore modifies basal Na+ entry. New information obtained under circumstances in which the membrane potential is maintained near 0 indicates that the true coupling stoichiometry is 2:1 rather than the commonly-accepted value of 1:1. A 2:1 stoichiometry means that cellular electrochemical Na+ gradients are adequate to account for recently observed 70-fold sugar gradients maintained by these cells under certain conditions.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D050260:Carbohydrate Metabolism; D002645:Chickens; D004848:Epithelium / Q000378:metabolism; D007408:Intestinal Absorption / Q000187:drug effects; D007700:Kinetics; D008564:Membrane Potentials; D008757:Methylglucosides / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D014634:Valinomycin / Q000494:pharmacology
D008757:Methylglucosides; D014634:Valinomycin; D012964:Sodium