Cocaine Inhibits Chloride Secretion by Swine Tracheal Submucosal Gland Cells Grown in Culture

Abstract

Active ion transport by airway submucosal gland cells plays an important role in maintaining effective mucociliary clearance. Alterations in the clearance will affect normal airway functions. Nasal and airway mucosal surfaces are exposed to high concentrations of cocaine after snorting crystals or smoking the freebase form, causing respiratory complications. The actions of cocaine on airway gland cell ion transport were determined by measuring the basal electrical properties and ion transport activated by acetylcholine (ACh) and isoproterenol (ISO) in swine tracheal submucosal gland cells grown in culture. The cells were enzymatically isolated, purified on Percoll density gradients, and then grown on microporous inserts at an air interface. Chloride secretion was measured as short-circuit current (Isc) utilizing Ussing chamber methodology. Amiloride (10 μm) was added mucosally to block sodium reabsorption. The maximal changes in Isc (ΔIsc) induced by ACh and ISO were 42.0 ± 4.4 and 8.8 ± 0.8 μA/cm2. Cocaine decreased basal Isc and the increase in Isc induced by ACh and ISO. The concentration–response relationships for ACh and ISO were shifted to the right by cocaine (1–3 mm) when applied serosally. The maximal increase in Isc induced by ISO was inhibited by serosal cocaine, but, the maximal response to ACh was not. Thus, cocaine inhibits ACh-induced increases in Isc by competitively blocking the receptor and the response to ISO by noncompetitive inhibition. Mucosal cocaine reduced the maximal response to ACh and ISO and also caused a rightward shift. We conclude that cocaine directly alters submucosal gland cell function by reducing the basal and stimulated ability to transport ions and fluid.