Cystic Fibrosis:  Modulation of Lung Mucus Secretion

Boat, Thomas

Abstract

We propose to continue investigations of mechanisms by which the secretory rate and types of mucous glycoprotein are modulated in large airways epithelium. Investigations will be carried out in vitro, using tracheobronchial tissue from cats, rabbits, and humans. The effect of autonomic agonists, antagonists and other biologically active substances will be tested alone and in combination. Secretory responses to these agents will be correlated with intracellular events such as changes in cyclic nucleotide levels, binding of cyclic nucleotides to proteins, and protein phosphorylation-dephosphorylation. These effects will be studied in intact tracheal tissue, in isolated surface epithelium, and in tracheal tissues from which surface epithelium has been removed. Baseline rates of secretion and responses to stimuli of various secretory cells will be followed by autoradiographic tracking of glycoprotein precursor uptake and movement through these cells. The chemical properties, especially the extent of sulfation, of glycoproteins secreted in response to different neurohumoral agents will be assessed. Finally, the mucus-simulating properties in cystic fibrosis (CF) serum will be studied in detail. The current assay system for this activity will be modified by prior fractionation of serum or by converting to radioimmunoassay of the mucous glycoproteins in an attempt to completely segregate CF, heterozygote, and control serum responses for clinical and/or genetic studies. Serum activity will be purified, and if possible, identified. We will conduct studies to determine which mechanism(s) mediate the serum effect and how this effect relates to physiological control. We anticipate that these studies will provide a basis for understanding the regulation of mucous glycoprotein secretion in the lung and how this system is perturbed in cystic fibrosis.