Metabolic energy dependence of glucose, water and sodium absorption in the presence and absence of 'downhill' sodium gradients across isolated rat small intestine.

1. Absorption of glucose and water was studied in isolated perfused rat small intestine with arterial infusion under normal conditions and with a 'downhill' sodium gradient across the mucosa. 2. The effects of metabolic inhibitors, iodoacetate phenformin and dinitrophenol, on absorption were determined in the presence of normal and 'downhill' sodium gradients. 3. Glucose absorption was inhibited by each inhibitor, and the inhibition was independent of the direction of the sodium gradient. 4. Net sodium flux across the mucosa was also inhibited under 'downhill' sodium gradient conditions. 5. The simultaneous and parallel inhibition of both glucose and sodium transport is consistent with, but does not prove, the sodium gradient theory.