Pathways for volume flow and volume regulation in leaky epithelia

G. Whittembury, A. Paz-Aliaga, Angela Biondi, Paola Carpi-Medina, E. González, H. Linares

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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, Poscb, is high; b) its activation energy, Ea, is as that of free water movement and c) pCMBS inhibits markedly (but reversibly)Poscb and increases Ea to values similar to those observed in lipid bilayers without pores. d) Preliminary measurements of Pd the water diffusive permeability coefficient using NMR indicate that Poscb/Pd 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 and Rhodnius 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.

Original languageEnglish
Pages (from-to)S17-S22
JournalPflugers Archiv European Journal of Physiology
Issue number1 Supplement
StatePublished - Mar 1985
Externally publishedYes


  • Cell membrane pores
  • Epithelial water transport
  • Kidney proximal tubule
  • Leaky epithelia
  • Osmotic equilibration
  • Paracellular water flow
  • Tubular permeability
  • Water osmotic permeability


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