Transepithelial potential difference
Open-knowledge reference entry
Transepithelial potential difference (TEPD) is the voltage across an epithelium, and is the sum of the membrane potentials for the outer and inner cell membranes.
TEPD in the nose
The diagnosis of cystic fibrosis (CF) is usually based on high chloride concentrations in sweat, characteristic clinical findings (including sinopulmonary infections), and/or family history. However, a small portion of patients with cystic fibrosis, especially those with "mild" mutations of the cystic fibrosis transmembrane regulator (CFTR) ion channel, have near-normal sweat tests.
In these cases, a useful diagnostic adjunct involves measuring the nasal transepithelial potential difference (i.e. the charge on the respiratory epithelial surface as compared to interstitial fluid). Individuals with cystic fibrosis have a significantly more negative nasoepithelial surface than normal, due to increased luminal sodium absorption.
In most exocrine glands, the CFTR protein normally secretes chloride ions into the lumen, and also has a tonic inhibitory effect on the opening of the apical sodium channel (which absorbs sodium into the cell). Impaired CFTR functioning directly reduces ductal epithelial chloride secretion and indirectly increases sodium absorption through lack of CFTR's inhibitory effect on the apical sodium channel. The result is dehydrated mucus and a widened, negative transepithelial potential difference.
The nasal TEPD is increased in cystic fibrosis, making it a potential diagnostic tool for this disorder.
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This entry incorporates text from “Transepithelial potential difference” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.