Conductance Pathways Involved in Chloride Secretion and Their Regulation
Cystic fibrosis impairs the secretory activities of a variety of exocrine glands and other secretory epithelia in the intestines and airways. The secretion of salt and water across epithelia of this type is driven by a secondary active Cl transport mechanism (Frizzell et al., 1979). Chloride enters secretory cells due to the combined activities of three basolateral membrane transport events: Na/K/Cl co-transporters, Na/K pumps, and K channels. Chloride leaves secretory cells across the apical membranes by diffusion, and alterations in apical Cl conductance represent a pivotal control point that determines Cl secretion rate. A variety of hormones and neurotransmitters stimulate salt secretion via their intracellular mediators, cAMP and Ca. The overall Cl secretory process is electrogenic so that the co-ion, Na, accompanies Cl to the lumen via paracellular pathways, driven by the lumen-negative voltage arising from Cl secretion.
KeywordsCystic Fibrosis Cystic Fibrosis Airway Outward Rectification Secretory Epithelial Cell Outward Rectifier
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