title: Comparison of transcellular and transepithelial water osmotic permeabilities (Pos) in the isolated proximal straight tubule (PST) of the rabbit kidney.
abstract: Measurements of the water osmotic permeabilities of apical and basolateral membranes of PST cells and of the transepithelial permeability have been carried out using a very fast method with high temporal and spatial resolution. At 25 degrees C the values obtained are: 80.8 +/- 11.9 x 10(-4) cm3/s osmol cm2 of apical (luminal) surface area and 90.1 +/- 13.0 x 10(-4) cm3/s osmol cm2 of basement membrane area (no membrane invaginations taken in account). These values are higher than previously published values due to the use of a faster and more accurate volume measuring and recording system. The transepithelial water osmotic permeability at 25 degrees C is 77 +/- 11 in units of 10(-4) cm3/s osmol cm2 basement membrane area. The transcellular water osmotic permeability is 32 +/- 7 (same units), leaving a paracellular contribution of 45 +/- 10 (same units). In the presence of 2.5 mM parachloromercuribenzenesulfonate (pCMBS) the apical permeability is reduced with an incubation of 10-15 min to 23% of its control value and the basolateral permeability to 8% of its control value (after 25 min) but the transepithelial permeability is only reduced to about 1/2 of the control value. This leaves a transcellular permeability of 6 x 10(-4) cm3/s osmol cm2 of basement membrane area and a paracellular contribution of 33 +/- 6 (same units). These results indicate a significant contribution of the paracellular pathway to the transepithelial water osmotic permeabilities in PST.
authors.affiliation: Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela.
authors.forename: P
authors.initials: P
authors.lastname: Carpi-Medina
authors.forename: G
authors.initials: G
authors.lastname: Whittembury
mesh_terms: D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D002463:Cell Membrane Permeability; D004848:Epithelium / Q000502:physiology / Q000648:ultrastructure; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D009995:Osmosis; D011817:Rabbits; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014867:Water / Q000493:pharmacokinetics*
chemical_list: D013439:Sulfhydryl Reagents; D014867:Water; D002731:4-Chloromercuribenzenesulfonate