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Missing Cl conductance in cystic fibrosis
The American Journal of Physiology
|October 1, 1986
Summary
Cystic fibrosis (CF) sweat ducts exhibit significantly lower epithelial conductance than normal ducts. This reduced conductance in CF is primarily due to a lack of chloride ion (Cl) channels, not altered sodium (Na) or other ion conductances.
Area of Science:
- Physiology
- Ion Transport
- Epithelial Biology
Background:
- Human eccrine sweat glands are crucial for thermoregulation.
- Cystic Fibrosis (CF) is a genetic disorder affecting ion transport.
- Eccrine sweat duct dysfunction is a hallmark of CF.
Purpose of the Study:
- To compare ion conductance in normal and CF sweat ducts.
- To elucidate the ionic basis of reduced sweat duct conductance in CF.
- To investigate the role of chloride (Cl) and sodium (Na) in sweat duct function.
Main Methods:
- Cable analysis of microperfused human eccrine sweat duct segments.
- Measurement of specific epithelial conductance (Gt).
- Pharmacological manipulation using amiloride and varying chloride concentrations.
Main Results:
- Normal (N) ducts showed a total conductance (Gt) of 125 mS/cm2, sixfold higher than CF ducts (15 mS/cm2).
- Chloride (Cl) removal reduced N duct Gt to CF duct levels, indicating Cl as the primary conductive ion.
- Amiloride affected N ducts differently in Cl-containing vs. Cl-free media, while its effect on CF ducts was consistent.
Conclusions:
- CF sweat duct epithelium exhibits near-complete absence of an electrodiffusive chloride (Cl) shunt.
- The reduced conductance in CF is specific to Cl, with other conductance components likely unaltered.
- Findings clarify the ion transport defect in CF sweat ducts.