Lung disease in cystic fibrosis (CF) arises from obstruction and destruction of small airways (bronchioles). A fluid layer over the inner bronchiolar epithelial surface is normally the first line of airway defense against inhaled pathogens. Since fluid transport in CF is defective and bronchioles invariably become infected in CF, it is evident that proper fluid transport is essential to respiratory health. Despite the importance of this conclusion, small airways have largely evaded studies of their native fluid transport components because it is very difficult to obtain intact bronchiolar epithelium without destroying it. Recently, we successfully applied techniques to small airways that we developed much earlier for microperfusing single sweat duct tubules. We propose here to determine the properties of fluid transport in freshly isolated native, intact epithelia of bronchioles. In contrast to the common notion that the same cells both secrete and absorb, we now have evidence that this epithelium is made up of distinct secretory and absorptive cells. This proposal will define the previously undetermined basic fluid transport properties of small airway epithelia and test the novel hypothesis that in small airways some cells secrete while others absorb fluid.
Three specific aims will use a combination of electrophysiological, RT-PCR gene expression assays, and immunocytochemistry to: 1.) optimize conditions and systems to preserve and examine bronchioles, 2.) determine basic absorptive and secretory properties of small airway epithelia, and 3.) show that there are functionally and structurally separate zones of absorptive and secretory cells in small airway epithelia. Lay Abstract: The genetic disease of cystic fibrosis (CF) is a rare form of obstructive lung disease in which the very small airways or bronchioles become so damaged and plugged with mucus that the patient dies. Normal bronchioles are hollow with a thin layer of fluid that coats their inner surfaces and helps remove inhaled debris, bacteria, and viruses. The basic problem in CF is abnormal fluid formation, which tells us that problems in the CF lung start in this fluid layer. Studies of small airways in their natural state are difficult, and very few have been attempted. We have applied a micro-method we used on small sweat gland tubes to study small intact bronchiole tubes. We propose to test a new finding that cells that secrete fluid are different from those that absorb fluid as opposed to the common idea that the same cells do both. This work may fundamentally change how we think about how normal bronchioles handle fluid and how bronchioles in CF and other forms of inflammatory lung diseases are destroyed. Correctly understanding this fundamental structure/function is critical to developing effective therapies. ? ? ?

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Lung Cellular, Molecular, and Immunobiology Study Section (LCMI)
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Banks-Schlegel, Susan P
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University of California San Diego
Schools of Medicine
La Jolla
United States
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Shamsuddin, A K M; Quinton, Paul M (2014) Native small airways secrete bicarbonate. Am J Respir Cell Mol Biol 50:796-804
Cooper, Jeffrey L; Quinton, Paul M; Ballard, Stephen T (2013) Mucociliary transport in porcine trachea: differential effects of inhibiting chloride and bicarbonate secretion. Am J Physiol Lung Cell Mol Physiol 304:L184-90
Yang, Ning; Garcia, Mary Abigail S; Quinton, Paul M (2013) Normal mucus formation requires cAMP-dependent HCO3- secretion and Ca2+-mediated mucin exocytosis. J Physiol 591:4581-93
Shamsuddin, A K M; Quinton, P M (2012) Surface fluid absorption and secretion in small airways. J Physiol 590:3561-74
Muchekehu, Ruth W; Quinton, Paul M (2010) A new role for bicarbonate secretion in cervico-uterine mucus release. J Physiol 588:2329-42
Quinton, Paul M (2010) Birth of mucus. Am J Physiol Lung Cell Mol Physiol 298:L13-4
Chen, Eric Y T; Yang, Ning; Quinton, Paul M et al. (2010) A new role for bicarbonate in mucus formation. Am J Physiol Lung Cell Mol Physiol 299:L542-9
Garcia, Mary Abigail S; Yang, Ning; Quinton, Paul M (2009) Normal mouse intestinal mucus release requires cystic fibrosis transmembrane regulator-dependent bicarbonate secretion. J Clin Invest 119:2613-22
Quinton, Paul M (2008) Cystic fibrosis: impaired bicarbonate secretion and mucoviscidosis. Lancet 372:415-7
Shamsuddin, A K M; Reddy, M M; Quinton, P M (2008) Iontophoretic beta-adrenergic stimulation of human sweat glands: possible assay for cystic fibrosis transmembrane conductance regulator activity in vivo. Exp Physiol 93:969-81