A Quantitative Analysis of Electrolyte Exchange in the Salivary Duct.

1The University of Auckland.
AJP Gastrointestinal and Liver Physiology (Impact Factor: 3.8). 08/2012; 303(10). DOI: 10.1152/ajpgi.00364.2011
Source: PubMed


A healthy salivary gland secretes saliva in two stages. First, acinar cells generate primary saliva, a plasma-like, isotonic fluid high in Na(+) and Cl(-). In the second stage, the ducts exchange Na(+) and Cl(-) for K(+) and HCO(3)(-), producing a hypotonic final saliva with no apparent loss in volume. We have developed a tool which aims to understand how the ducts achieve this electrolyte exchange while maintaining the same volume. This tool is part of a larger multi-scale model of the salivary gland and can be used at the duct or gland level, to investigate the effects of genetic and chemical alterations. In this paper, we construct a radially symmetric mathematical model of the mouse salivary gland duct, representing the lumen, the cell and the interstitium. For a given flow and primary saliva composition, we predict the potential differences and the luminal and cytosolic concentrations along a duct. Our model accounts well for experimental data obtained in wild type animals as well as knockouts and chemical inhibitors. Additionally, the luminal membrane potential of the duct cells is predicted to be very depolarized in comparison to acinar cells. We investigate the effects of an electrogenic vs electroneutral anion exchanger in the luminal membrane on concentration and the potential difference across the luminal membrane as well as how impairing the CFTR channel affects other ion transporting mechanisms. Our model suggests the electrogenicity of the anion exchanger has little effect in the submandibular (SMG) duct.

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Available from: Marcelo A Catalán
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