ATP and A1 adenosine receptor agonists mobilize intracellular calcium and activate K+ and Cl- currents in normal and cystic fibrosis airway epithelial cells

The effect of purinergic compounds on [Ca2+](i) and membrane currents of cell lines derived from the airway epithelium of normal and cystic fibrosis individuals has been investigated. 2-Chloroadenosine (2-CADO), as well as other agonists of the A1 adenosine receptors, causes a transient elevation of cytosolic [Ca2+] that is antagonized by the A1 adenosine receptor antagonist 8-cyclopentyl-1,3 dipropylxanthine (DPCPX). ATP is also effective, but at a lower extent. The [Ca2+](i) increase induced by 2-CADO and ATP is abolished by preincubation with phorbol 12-myristate 13-acetate and the Ca2+-ATPase inhibitor thapsigargin. This latter result suggests that purinergic agonists mobilize Ca2+ from inositol 1,4,5-trisphosphate- sensitive stores. Pertussis toxin completely inhibits the effect of 2-CADO, whereas only it partially affects that of ATP, suggesting the involvement of different types of G proteins. Perforated patch clamp experiments carried out in both current clamp and voltage clamp modes show that 2-CADO and ATP activate K+- and Cl--selective membrane currents, with a mechanism inhibited by preincubation with DPCPX and thapsigargin. These data indicate that activation of adenosine A1 receptor, in a similar way to ATP receptor, causes [Ca2+](i) increase and ion channels activation through a transduction mechanism that is not impaired in cystic fibrosis airway epithelial cells.