EFFECT OF CHANGING INTESTINAL FLOW-RATE ON A MEASUREMENT OF INTESTINAL PERMEABILITY

Background/Aims: The flow rate of fluid through the proximal small int estine varies widely under normal physiological conditions. The aim of this study was to assess the effect of changes in flow rate on the pa ssive permeability of the aqueous paracellular pathway of the human je junum. Methods: Normal subjects were studied in vivo during constant p erfusion of 30-cm loops of jejunum at flow rates of 5, 10, or 20 mL/mi n. The permeability ratio of L-xylose/urea was used to assess apparent permeability of the mucosa and to calculate the average pore radius o f the aqueous pathway for passive diffusion. Results: Increasing jejun al flow rate from 5 to 20 mL/min significantly decreased the L-xylose/ urea permeability ratio from 0.35 to 0.23 and decreased average calcul ated pore radius of the diffusion pathway from 13 Angstrom to 8 Angstr om. Conclusions: Increases in Row rate in the normal physiological ran ge decrease the estimated pore size of normal healthy jejunal mucosa. Because increasing flow rate is known to increase exposure of luminal fluid to the intervillus space, the results of this study ave best exp lained by postulating that cells lining the sides of villi are less pe rmeable than cells lining the villus tips.