title: Adenosine receptors on human airway epithelia and their relationship to chloride secretion.
abstract: 1. We have characterized an adenosine receptor subtype present in human airway epithelial cells by measuring the changes in the intracellular levels of adenosine 3':5'-cyclic monophosphate (cyclic AMP) and the rate of transepithelial Cl- secretion. 2. Primary cultures of human nasal epithelium obtained from excised surgical airway epithelial tissues and the cell lines BEAS39 and CF/T43 derived from human airway epithelium were grown on plastic dishes and labelled with [3H]-adenine for measurement of intracellular cyclic AMP accumulation. Primary cultures were loaded with the calcium indicator fura-2 to measure [Ca2+]i and studied as polarized, ion transporting epithelia on collagen matrix supports for measurement of Cl- secretion. 3. Adenosine analogues stimulated cyclic AMP accumulation with a rank order of potency characteristic of an A2-receptor: 5-N-ethyl-carboxamidoadenosine (NECA) greater than adenosine greater than R-phenylisopropyladenosine (R-PIA), 6-N-cyclopentyladenosine (CPA) greater than S-PIA. NECA increased cyclic AMP accumulation in normal and cystic fibrosis (CF) primary cells as well as in the CF/T43 and BEAS39 cell lines with K0.5 values ranging from 0.3 to 3 microM. Preincubation with NECA resulted in the homologous desensitization of airway epithelial cells. The effect of NECA was specifically inhibited by the adenosine receptor antagonist, aminophylline, in a competitive manner. 4. The A1-adenosine receptor agonists CPA and R-PIA did not inhibit isoprenaline-stimulated cyclic AMP accumulation in CF/T43 cells, and potentiating effects of the adenosine analogues were observed on forskolin-stimulated cyclic AMP accumulation. Adenosine analogues did not cause significant changes in intracellular Ca2+ ([Ca2+]i) in airway epithelium.5. Adenosine analogues, applied to either the serosal or mucosal side of the polarized amiloride pretreated primary cultures, induced changes in I,, with a rank order of potency of agonists similar to that observed for stimulation of cyclic AMP accumulation. Intracellular microelectrode studies indicated that the locus of action was the apical membrane Cl- conductance. Adenosine failed to stimulate C1- secretion in CF airway epithelium.6. These results provide evidence for the existence of an A2-adenosine receptor that modulates intracellular levels of cyclic AMP in human airway epithelium. Activation of this receptor might lead to stimulation of Cl- secretion in amiloride pretreated normal but not CF cells.
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill 27599.
authors.forename: E R
authors.initials: ER
authors.lastname: Lazarowski
authors.forename: S J
authors.initials: SJ
authors.lastname: Mason
authors.forename: L
authors.initials: L
authors.lastname: Clarke
authors.forename: T K
authors.initials: TK
authors.lastname: Harden
authors.forename: R C
authors.initials: RC
authors.lastname: Boucher
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000628:Aminophylline / Q000494:pharmacology; D002118:Calcium / Q000032:analysis; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000032:analysis / Q000502:physiology; D004848:Epithelium / Q000737:chemistry; D006801:Humans; D011983:Receptors, Purinergic / Q000032:analysis / Q000502:physiology*; D012137:Respiratory System / Q000737:chemistry*; D014316:Tritium
chemical_list: D002712:Chlorides; D011983:Receptors, Purinergic; D014316:Tritium; D005576:Colforsin; D000628:Aminophylline; D000242:Cyclic AMP; D000241:Adenosine; D002118:Calcium