Fig. 2
From: Basal Nucleotide Levels, Release, and Metabolism in Normal and Cystic Fibrosis Airways
Constitutive ATP release from cultured airway cells. (A) The basal ATP concentration and [32P]γATP mass measured in the mucosal bath of cultured cystic fibrosis (CF) tracheobronchial epithelial cells. values represent the percent of initial values, obtained from three cultures from a CF patient. A trace quantity of [32P]γATP was added to the apical media overlying well-differentiated tracheobronchial cells that had been undisturbed for 3 hr. Sequential samples were analyzed for ATP concentration using the luciferin-luciferase assay, and [32P]γATP metabolism was measured with high performance liquid chromatography (HPLC). ATP concentration (open circles) remained constant despite ongoing ATP metabolism, as shown by the breakdown of [32P]γATP (closed squares). The simultaneous measurement of ATP concentration and initial [32P]γATP metabolic rate allowed calculation of the ATP release rate under these equilibrium conditions. (B) The mean calculated rate of constitutive ATP release (± standard error of the mean; SEM) from normal (3 patients; 3–6 cultures/patient) and CF (2 patients; 3–6 cultures/patient) airway cells.