Purinoceptor activation of chloride transport in cystic fibrosis and CFTR-transfected pancreatic cell lines

Abstract

1. The regulation of chloride efflux from cystic fibrosis pancreatic adenocarcinoma cells (CFPAC-1) and wild-type CFTR-transfected CFPAC-1 cells (TPAC) was compared.

2. Forskolin (10 μM) stimulated chloride efflux from the corrected TPAC cells but not from CFPAC-1 cells. Chloride efflux from both cell types was activated by thapsigargin (0.5 μM).

3. The nucleotides ATP and UTP and the non-hydrolyzable ATP analogue, adenosine 5′-O-(3-thio) triphosphate (ATPγS), stimulated chloride efflux from both cell types. None of the other P₂ purinoceptor agonists investigated elicited a response. The order of potency was ATP⩾UTP⩾ATPγS.

4. Adenosine (10–100 μM) activated choride efflux from the TPAC but not the CFPAC cell line with no increase in intracellular cyclic AMP. Small but statistically significant inhibitions of the adenosine-(50 μM)-stimulated increase in chloride efflux were elicited by the A₁ receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (CPX, 100 nM) and the A₂ receptor antagonist 3,7-dimethyl-1-propylargylxanthine (DMPX, 10 μM). The A_2A receptor antagonist 8-(3-chlorostyryl)caffeine (CSC, 100 nM) had no significant effect.

5. These results provide evidence for the regulation of chloride efflux by P2Y₂ purinoceptors in genetically-corrected and CF pancreatic cell lines. Studies with adenosine receptor antagonists indicate some possible involvement of A₁ and A₂ (but not A_2A) receptors in the adenosine stimulation of chloride efflux, but the relatively small effects of the inhibitors coupled with lack of increase in cyclic AMP and a response only in the CFTR-transfected cells also suggests a possible direct effect of adenosine on CFTR.

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