Electrogenic transport of glucose in the normal upper duodenum. I. Technique and apparent transport constants

We investigated the electrogenic transport of glucose in the upper part of the duodenum in 11 healthy subjects by means of simultaneous intestinal perfusion of test solutions and measurement of the corresponding potential differences between blood and the duodenal lumen. The technique entailed continuous perfusion and registration of potentials through one single lumen of the probe. The basal potential difference during infusion of 154 mM NaCl was -4.9 +/- 0.5 mV (mean +/- 1 SEM). This was not significantly different from the level obtained during infusion of a standard perfusate composed like plasma: -4.3 +/- 0.5 mV. Perfusion of iso-osmolar solutions containing increasing concentrations of glucose raised the transmucosal potential difference progressively. The relation followed Michaelis-Menten kinetics, from which the apparent transport constants were calculated: Kappm = 53 mM and Vappmax = 9.9 mV. By means of repeated experiments, we examined day-to-day changes of basal potentials and electrogenic glucose transport. No significant differences or systematic variations were found.