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MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Ion transport across CF and normal murine olfactory and ciliated epithelium

Cystic Fibrosis/Pulmonary Research and Treatment Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina

Submitted 10 November 2008 ; accepted in final form 24 March 2009

The nasal epithelium of the cystic fibrosis (CF) mouse has been used extensively in CF research because it exhibits ion transport defects similar to those of human CF airways. This tissue is composed of 50% olfactory (OE) and 50% ciliated epithelium (CE), and on the basis of previous observations, we hypothesized that a significant fraction of the bioelectric signals from murine nasal tissue may arise from OE rather than CE, while CE is the target tissue for CF gene therapy. We compared the bioelectric properties of isolated OE from the nasal cavity and CE from the nasopharynx in Ussing chamber studies. Hyperabsorption of Na⁺ [amiloride response; CF vs. wild type (WT)] was 7.5-fold greater in the OE compared with the CE. The forskolin response in native tissues did not reliably distinguish genotypes, likely due to a cyclic nucleotide-gated cation conductance in OE and a calcium-mediated Cl^– conductance in CE. By potential difference assay, hyperabsorption of Na⁺ (CF vs. WT) and the difference in response to apical 0 Cl^– buffer (CF vs. WT) were 2-fold greater in the nasal cavity compared with the nasopharynx. Our studies demonstrate that in the CF mouse, both the hyperabsorption of Na⁺ and the Cl^– transport defect are of larger magnitude in the OE than in the CE. Thus, while the murine CF nasal epithelium is a valuable model for CF studies, the bioelectrics are likely dominated by the signals from the OE, and assays of the nasopharynx may be more specific for studying the ciliated epithelium.

chloride transport; nasal potential difference; sodium transport; cystic fibrosis