The effect of potassium on the intestinal transport of glucose.

The rate of absorption of glucose, galactose, and 3-0-methylglucose was studied in the rat's small intestine perfused in situ with isosmotic solutions containing these sugars and Na(2)SO(4) or K2SO(4). The presence of high [K(+)] in the lumen enhances absorption of glucose but not that of galactose or of 3-0-methylglucose. The potassium stimulation is apparent at higher glucose concentrations where primarily carrier-mediated diffusion is involved in the translocation. In this case potassium stimulates transport even if it is the only cation in the lumen. The potassium-stimulated intestine produces more glycogen with higher specific activity than the control gut. Lactic acid production by the intestine is markedly enhanced if the intestinal lumen is perfused with a solution containing glucose and high [K(+)]. It is concluded that potassium does not affect permeability or the specific sugar transport system of the gut, but enhances intracellular metabolic disappearance of glucose thereby creating a larger luminal intracellular concentration gradient which in turn enhances the rate of carrier-facilitated entry.