PMID: 2484000Jan 1, 1987Paper

Channels for water flow in epithelia: characteristics and regulation

Acta Physiologica Et Pharmacologica Latinoamericana : Organo De La Asociación Latinoamericana De Ciencias Fisiológicas Y De La Asociación Latinoamericana De Farmacología
G WhittemburyE González

Abstract

Pos and Pd, osmotic and diffusive water permeability coefficients of isolated rabbit proximal tubule (PT) cells (expressed per cm2 of real cell membrane area, in microns/sec) are: Pos 396; Pd, 22; Pos/Pd, 18 (control), and after exposure to parachloromercuribenzenesulfonate (pCMBS): Pos, 32; Pd, 10; Pos/Pd, 3. The sulfhydryl reagent dithiothreitol (DTT) reverts pCMBS action. The activation energies (kcal/mol) are Pos, 3.2 (control); 9.2 (pCMBS); Pd, 5.2 (control) and 9.1 (pCMBS). Thus water channels pierce the control plasma membrane and are reversibly closed by pCMBS. High control PT permeabilities are comparable with those of amphibian urinary bladder and collecting tubules (CT) stimulated with antidiuretic hormone (ADH), and low PT (pCMBS) values with those of CT in the resting state, respectively. Transcellular permeability is regulated in PT by the state of sulfhydryl groups and in CT by ADH induced insertion (or, no ADH, suppression) of water channels. In PT (a) large extracellular markers are dragged by water flow indicating extracellular solute-water interaction, (b) transepithelial Pos is much higher than transcellular Pos. Therefore water also flows paracellularly, in addition to the transcellular flow. In PT paracell...Continue Reading

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