Do pulmonary ionocytes absorb chloride or secrete chloride?
Ian M Thornell1, Lei Lei2, Paul B McCray2,3
1Department of Internal Medicine, Pappajohn Biomedical Institute, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States.
Abstract:
Pulmonary ionocytes express high levels of cystic fibrosis transmembrane conductance regulator (CFTR) channels. When studied using the short-circuit current technique, ionocytes produce CFTR-dependent short-circuit currents consistent with Cl- secretion. However, when studied without a voltage clamp, data indicate that ionocytes absorb Cl-. In this review, we resolve these seemingly conflicting findings by considering the different transepithelial voltages and the resultant movement of Cl- during short circuit and physiological open-circuit conditions. This analysis indicates that behavior under short-circuit conditions cannot be directly extrapolated to infer behavior under physiologic conditions. Finally, we discuss the potential role of basolateral Cl- channels in controlling absorption and secretion in ionocytes.
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