HUMAN SUBMUCOSAL GLAND AND BRONCHIOLAR SECRETIONS

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DESCRIPTION (Taken directly from the application) Cystic fibrosis (CF) bronchial epithelial cells have decreased Cl permeability and increased Na+ absorption, which may contribute to the abnormal airway secretions and secondary infection that typifies CF. Submucosal glands express high levels of CFTR mRNA and protein, and bronchioles are the site of earliest airway obstruction in CF, but the contributions of these structures to airway secretions and fluid balance in normal and CF lungs are not known. This research project will assess the contributions of bronchial submucosal glands and bronchiolar epithelium to fluid and mucus balance in normal and cystic fibrosis human airways. Human bronchial submucosal glands and bronchiolar epithelium from lungs removed from non-CF and CF patients during clinically indicated lung resection and transplant operations will be evaluated. The structure of submucosal glands and cellular distribution of bronchioles will be assessed by morphometric techniques and markers specific for submucosal gland serous cells, mucous cells, and ciliated cells, and morphologic criteria for collecting ducts and ciliated ducts. Bronchiolar epithelial cells will be identified as ciliated, goblet, or Clara on the basis of specific antibody recognition. The expression and cellular location of the ion transport proteins CFTR and alpha, beta, and gamma subunits of the human epithelial Na+ channel will be determined by in situ hybridization and immunohistochemistry. Submucosal gland secretion volume, ion composition, and regulation will be measured using volume pipettes, ion-selective microelectrodes, and a human mucin-specific ELISA. Bronchiolar epithelial potential difference, airway surface liquid ion content, and ion transport regulation will be assessed with in vivo potential difference electrometers, ion-selective microelectrodes, and transport agonists and inhibitors. These morphometric, gene localization, and physiologic approaches will permit us to test the hypothesis that submucosal gland secretions are decreased in quantity in cystic fibrosis and to localize the bronchiolar region in which major salt and water absorption takes place. This improved understanding of human submucosal gland and bronchiolar physiology may elucidate mechanisms that are abnormal in cystic fibrosis and amenable to novel therapeutic approaches.