F K Li1, C H To, J K Leung, T M Chan, K N Lai. 1. University Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Pokfulam. fkli@hku.hk
Abstract
OBJECTIVE: To elucidate ionic and glucose transport across human peritoneal mesothelium, we utilized an Ussing chamber setup and studied the electrophysiological characteristics and tissue permeabilities of human peritoneal mesothelial cells (HPMC) to L- and D-glucose. METHODS: Human mesothelial cells were grown on polyester filters (snapwell; Costar, Cambridge, MA, U.S.A.) that, upon confluence, were fitted into Ussing chambers. Transmesothelial resistance and resting potential were determined using electrophysiological techniques. Radiolabeled glucose was added to one side of the chamber and the permeabilities determined by serial sampling in the receptive compartment. RESULTS: The transmesothelial potential and resistance were 0.54 +/- 0.07 mV (apical positive) and 20.4 +/- 3.2 ohms x cm2 respectively (mean +/- SEM, n = 36). The course of overall transfer of D- and L-glucose was examined using L-glucose as a positive diffusion-plus-leak marker. The permeabilities of HPMC to D-glucose were 3.00 +/- 0.26 cm/sec (apical-to-basolateral) and 3.25 +/- 0.27 cm/sec (basolateral-to-apical) [n = 6 experiments, p = not significant (NS)], which were not different from those of L-glucose: 3.00 +/- 0.30 cm/sec (apical-to-basolateral) and 2.71 +/- 0.24 (basolateral-to-apical) (n = 6 experiments, p = NS). CONCLUSIONS: The transepithelial resistance of HPMC is low and the ionic gradient, although it exists, is small and inconsequential. Passive paracellular flow accounts for the majority of transmesothelial glucose transport. The existence of a large paracellular shunt precludes the mesothelial membrane as a clinically relevant osmotic barrier.
OBJECTIVE: To elucidate ionic and glucose transport across human peritoneal mesothelium, we utilized an Ussing chamber setup and studied the electrophysiological characteristics and tissue permeabilities of human peritoneal mesothelial cells (HPMC) to L- and D-glucose. METHODS:Human mesothelial cells were grown on polyester filters (snapwell; Costar, Cambridge, MA, U.S.A.) that, upon confluence, were fitted into Ussing chambers. Transmesothelial resistance and resting potential were determined using electrophysiological techniques. Radiolabeled glucose was added to one side of the chamber and the permeabilities determined by serial sampling in the receptive compartment. RESULTS: The transmesothelial potential and resistance were 0.54 +/- 0.07 mV (apical positive) and 20.4 +/- 3.2 ohms x cm2 respectively (mean +/- SEM, n = 36). The course of overall transfer of D- and L-glucose was examined using L-glucose as a positive diffusion-plus-leak marker. The permeabilities of HPMC to D-glucose were 3.00 +/- 0.26 cm/sec (apical-to-basolateral) and 3.25 +/- 0.27 cm/sec (basolateral-to-apical) [n = 6 experiments, p = not significant (NS)], which were not different from those of L-glucose: 3.00 +/- 0.30 cm/sec (apical-to-basolateral) and 2.71 +/- 0.24 (basolateral-to-apical) (n = 6 experiments, p = NS). CONCLUSIONS: The transepithelial resistance of HPMC is low and the ionic gradient, although it exists, is small and inconsequential. Passive paracellular flow accounts for the majority of transmesothelial glucose transport. The existence of a large paracellular shunt precludes the mesothelial membrane as a clinically relevant osmotic barrier.