Water does not flow across the tight junctions of MDCK cell epithelium

Kovbasnjuk, Olga; Leader, John P.; Weinstein, Alan M.; Spring, Kenneth R.

doi:10.1073/pnas.95.11.6526

Cited by 74 publications

(46 citation statements)

References 13 publications

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“…Since the discovery of aquaporin (AQP) water channels in both epithelial cell membranes, the molecular basis of a transcellular pathway has been evident . By contrast, the contribution of the paracellular pathway through the tight junctions (TJ) was estimated to be between 0 and 100%, depending on the method used for analysis (Kovbasnjuk et al, 1998;Quigley and Baum, 2002;Shachar-Hill and Hill, 2002;Spring, 1998;Zeuthen, 1995). Although TJs are often named aqueous pores, there is, as yet, no direct experimental evidence of paracellular water flux.…”

Section: Introductionmentioning

confidence: 99%

“…Apart from analytical calculations (Weinstein and Stephenson, 1981a;Weinstein and Stephenson, 1981b), two experimental approaches have been reported: the fluidphase fluorescent tracer technique in combination with confocal microscopy (Segawa et al, 2002) and optical methods for visualizing fluid movement in the lateral intercellular space (Kovbasnjuk et al, 1998). These investigations yielded, in part, contrasting results.…”

Section: Introductionmentioning

confidence: 99%

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Claudin-2, a component of the tight junction, forms a paracellular water channel

Rosenthal

Milatz

Krug

et al. 2010

Journal of Cell Science

373

330

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SummaryWhether or not significant amounts of water pass the tight junction (TJ) of leaky epithelia is still unresolved, because it is difficult to separate transcellular water flux from TJ-controlled paracellular water flux. Using an approach without differentiating technically between the transcellular and paracellular route, we measured transepithelial water flux with and without selective molecular perturbation of the TJ to unequivocally attribute changes to the paracellular pathway. To this end, MDCK C7 cells were stably transfected with either claudin-2 or claudin-10b, two paracellular cation-channel-forming TJ proteins that are not endogenously expressed in this cell line. Claudin-2 is typical of leaky, water-transporting epithelia, such as the kidney proximal tubule, whereas claudin-10b is present in numerous epithelia, including water-impermeable segments of the loop of Henle. Neither transfection altered the expression of endogenous claudins or aquaporins. Water flux was induced by an osmotic gradient, a Na + gradient or both. Under all conditions, water flux in claudin-2-transfected cells was elevated compared with vector controls, indicating claudin-2-mediated paracellular water permeability. Na + -driven water transport in the absence of an osmotic gradient indicates a single-file mechanism. By contrast, claudin-10b transfection did not alter water flux. We conclude that claudin-2, but not claudin-10b, forms a paracellular water channel and thus mediates paracellular water transport in leaky epithelia.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Claudin-2, a component of the tight junction, forms a paracellular water channel

Rosenthal

Milatz

Krug

et al. 2010

Journal of Cell Science

373

330

View full text Add to dashboard Cite

show abstract

“…1 describes water flow via a transcellular pathway as found by Rivers et al (1996) who studied populations of MDCK cysts. This was also found to be the case by Kovbasnjuk et al (1998) who developed an optical microscopic technique to visualize the flow velocity profiles within the lateral intercellular spaces and to test for fluid flow across the tight junction. The flow velocity within the lateral intercellular spaces fell almost to zero adjacent to the tight junction, indicating that transjunctional flow can be neglected.…”

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confidence: 96%

A model for cyst lumen expansion and size regulation via fluid secretion

Gin

Tanaka

Brusch

2010

Journal of Theoretical Biology

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“…However, there is a precedent for a completely transcellular flow of water in an electrically 'leaky' epithelium. Using a direct visualization technique, Kovbasnjuk and colleagues reported that water did not flow through the paracellular pathway in an MDCK (renal) cell epithelium, even when osmotic gradients were applied (Kovbasnjuk et al, 1998). However, the situation in the killifish gut appears to be very different from that in the mammalian gut where much of the increased intestinal water absorption accompanying a meal appears to be paracellular, and serves to drive the paracellular absorption of ions and nutrients by convective solvent drag, at minimal metabolic cost (Pappenheimer and Reiss, 1987;Madara and Pappenheimer, 1987).…”

Section: Differences Between Euryhaline Fish and Mammalsmentioning

confidence: 99%

Independence of net water flux from paracellular permeability in the intestine ofFundulus heteroclitus, a euryhaline teleost

Wood

Grosell

2012

Journal of Experimental Biology

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SUMMARYParacellular permeability and absorptive water flux across the intestine of the euryhaline killifish were investigated using in vitro gut sac preparations from seawater-and freshwater-acclimated animals. The permeability of polyethylene glycol (PEG), a wellestablished paracellular probe, was measured using trace amounts of radiolabelled oligomers of three different molecular sizes (PEG-400, PEG-900 and PEG-4000) at various times after satiation feeding. All three PEG molecules were absorbed, with permeability declining as a linear function of increasing hydrodynamic radius. Response patterns were similar in seawater and freshwater preparations, though water absorption and PEG-900 permeability were greater in the latter. Despite up to 4-fold variations in absorptive water flux associated with feeding and fasting (highest at 1-3h, lowest at 12-24h and intermediate at 1-2weeks post-feeding), there were no changes in PEG permeability for any size oligomer. When PEG permeability was measured in the opposite direction (i.e. serosal to mucosal) from net water flux, it was again unchanged. HgCl 2 (10 -3 moll -1 ), a putative blocker of aquaporins, eliminated absorptive water flux yet increased PEG-4000 permeability by 6-to 8-fold in both freshwater and seawater preparations. Experimentally raising the serosal osmolality by addition of 300mmoll -1 mannitol increased the absorptive water flux rate 10-fold, but did not alter PEG permeability. Under these conditions, HgCl 2 reduced absorptive water flux by 60% and again increased PEG permeability by 6-to 8-fold in both freshwater and seawater preparations. Clearly, there was no influence of solvent drag on PEG movement. The putative paracellular blocker 2,4,6-triaminopyrimidine (TAP, 20mmoll -1 ) had no effect on net water flux or PEG permeability. We conclude that PEG and water move by separate pathways; absorptive water transport probably occurs via a transcellular route in the intestine of Fundulus heteroclitus.

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Water does not flow across the tight junctions of MDCK cell epithelium

Cited by 74 publications

References 13 publications

Claudin-2, a component of the tight junction, forms a paracellular water channel

Claudin-2, a component of the tight junction, forms a paracellular water channel

A model for cyst lumen expansion and size regulation via fluid secretion

Independence of net water flux from paracellular permeability in the intestine ofFundulus heteroclitus, a euryhaline teleost

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