ISSN:
1432-2013
Keywords:
Water osmotic permeability
;
Leaky epithelia
;
Paracellular water flow
;
Osmotic equilibration
;
Cell membrane pores
;
Tubular permeability
;
Epithelial water transport
;
Kidney proximal tubule
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Continuous pathways must pierce the cell membrane to be used by water during osmotic equilibration between proximal straight tubular cells and the external medium, because a) the water osmotic permeability coefficient of the basolateral plasma membrane,P os cb , is high; b) its activation energy,E a, is as that of free water movement and c) pCMBS inhibits markedly (but reversibly)P os cb and increasesE a to values similar to those observed in lipid bilayers without pores. d) Preliminary measurements ofP d the water diffusive permeability coefficient using NMR indicate thatP os cb /P d is near 4–5. The following two observations indicate that a significant paracellular water flow must exist in leaky epithelia. Namely, a) large extracellular solutes are dragged by water in four leaky epithelia: gall bladder, Necturus proximal tubule, rat proximal tubule andRhodnius malpighian tubule. b) The transcellular water osmotic permeability coefficient is smaller than the transepithelial values available in the rabbit proximal straight tubule. This requires a significant paracellular permeability.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00581774
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