Osmotic water permeability of the apical membrane of proximal straight tubular (PST) cells |
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Authors: | Ernesto Gonzáles Paola Carpi-Medina Henry Linares Guillermo Whittembury |
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Institution: | (1) Centro de Biofisica y Bioquímica, Instituto Venezolano de Investigaciones Científicas, IVIC, Caracas, Venezuela;(2) Escuela de Medicina J. M. Vargas, UCV, Caracas, Venezuela |
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Abstract: | Osmotic steps, C, were produced across the apical cell membrane of isolated rabbit PST by perfusing their lumens with double barreled micropipettes at a rate of 0.5–0.8 nl/s. C=15–46 mOsmolar were induced with mannitol. Changes in luminal diameter were recorded as a function of time with a TV camera and an integrator-processor system with space and time resolutions of 0.03 m and 0.0167 s (3). The tubules were bathed with oil. Outer tubule diameter was time invariant. P
os
ca
, the apical cell osmotic permeability was therefore calculated from cell volume changes with time in units of 10–4 cm3/cm2. s. Osmolar. P
os
ca
was independent of C. The mean is 22.8±1.3 (n=55). With a basolateral permeability of 50.4 (3,12), the transcellular permeability is 14 (same units) smaller than the transepithelial values available. This leads to the conclusion that a significant paracellular water osmotic permeability must exist. |
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Keywords: | Osmotic water permeability leaky epithelia kidney tubule cell water permeability apical permeability water transport ion transport |
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