Water permeability in different epithelial barriers

Abstract

The water permeability properties of a series of epithelial barriers (the toad urinary bladder [TUB], the rat caecum [RC], the distal human colon [DHC], and the human amnion [HA] were studied in different experimental conditions. Three parameters were simultaneously determined: the water permeability coefficient in the presence of a transepithelial hydrostatic gradient (Phydr); the water permeability coefficient in the presence of an osmotic gradient (Posm); and the transepithelial potential difference (dV). All experiments were performed with the same experimental device, allowing comparison of the permeability properties of the barriers tested. The results obtained were: (1) TUB (N=8): Phydr = 0.079±0.008 cm/s; Posm = 0.0004±0.0002 cm/s; dV=31±5 mV; (2) TUB after ADH (N=8): Phydr = 0.093±0.012 cm/s; Posm = 0.0065±0.0011 cm/s; dV=52±8; (3) RC (N=10): Phydr = 0.18±0.02 cm/s; Posm = 0.0019±0.0004 cm/s; dV=3.9±0.1 mV; (4) RC adapted to a high K diet (N=10): Phydr = 0.21±0.02 cm/s; Posm = 0.0018±0.0006 cm/s; dV=4.5±0.5 mV; (5) DHC (N=6): Phydr = 0.22±0.03 cm/s; Posm = 0.002±0.05 cm/s; dV=15±3 mV; (6) HA (N=10): Phydr = 0.32±0.05 cm/s; Posm = 0.0154±0.0015; dV=0. The results show a good correlation between Phydr and dV, but not between dV and Posm or between Posm and Phydr.