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Stimulation of chloride secretion by P 1 purinoceptor agonists in cystic fibrosis phenotype airway epithelial cell line CFPEo‐
Author(s) -
Chao Anthony C.,
Zifferblatt Jonathan B.,
Wagner John A.,
Dong Y.J.,
Gruenert Dieter C.,
Gardner Phyllis
Publication year - 1994
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1994.tb13047.x
Subject(s) - adenosine , agonist , medicine , endocrinology , cystic fibrosis transmembrane conductance regulator , adenosine receptor , biology , potency , cystic fibrosis , chemistry , pharmacology , receptor , biochemistry , in vitro
1 P 1 purinoceptor agonists like adenosine have been shown to stimulate Cl −1 transport in secretory epithelia. In the present study, we investigated whether P 1 agonist‐induced Cl −1 secretion is preserved in cystic fibrosis airway epithelium and which signalling mechanism is involved. The effects of purinoceptor agonists on Cl −1 secretion were examined in a transformed cystic fibrosis airway phenotype epithelial cell line, CFPEo‐. 2 Addition of adenosine (ADO; 0.1 – 1 m m ) markedly increased 125 I efflux rate. The rank order of potency of purinoceptor agonists in stimulating 125 I efflux was ADO > AMP > ADP ≃ ATP. A similar order of potency was seen in transformed cystic fibrosis nasal polyp cells, CFNPEo‐ (ADO > ATP > AMP > ADP). These results are consistent with the activation of Cl −1 secretion via a P 1 purinoceptor. 3 The P 1 agonists tested (at 0.01 and 0.1 m m ) revealed a rank order of potency of 5′‐N‐ethylcarboxamine adenosine (NECA) > 2‐chloro‐adenosine (2‐Cl‐ADO) > R ‐phenylisopropyl adenosine ( R ‐PIA). 4 The known potent A 2 adenosine receptor (A 2 AR) agonist, 5′‐(N‐cyclopropyl) carboxamidoadenosine (CPCA, 2 μ m ) but not the A 1 adenosine receptor agonist, N 6 ‐phenyl adenosine (N 6 ‐phenyl ADO, 10 μ m ) markedly increased 125 I efflux rate (baseline, 5.9 ± 2.0% min −1 , + CPCA, 10.9 ± 0.6% min −1 ; P < 0.01). The stimulant effect of CPCA (10 μ m ) was abolished by addition of the A 2 AR antagonist 3,7‐dimethyl‐1‐propargylxanthine (DMPX) (100 μ m ; reported K 1 = 11 ± 3 μ m ). These results favour the involvement of A 2 AR. 5 ADO (0.1 – 1 m m ) and CPCA (2 μ m ) both induced a marked increase in intracellular [Ca 2+ ] ([Ca 2+ ] i ); the effect of the latter was again abolished by pretreatment of the cells with DMPX. By contrast, N 6 ‐phenyl ADO did not affect [Ca 2+ ] i . 6 In patch‐clamp experiments, ADO (1 m m ) induced an outwardly‐rectified whole‐cell Cl −1 current (baseline, 2.5 ± 0.8 pA pF −1 , + ADO, 78.4 ± 23.8 pA pF −1 ; P < 0.02), which was largely inhibited in cells internally perfused with a selective inhibitory peptide of the multifunctional Ca 2+ /calmodulin‐dependent protein kinase, CaMK [273–302] (20 μ m ), as compared to a control peptide, CaMK [284–302]. Addition of BAPTA (10 m m ), a Ca 2+ chelator, to the perfusion pipette also abolished the ADO‐elicited Cl −1 current. 7 In conclusion, our results suggest that A 2 AR participates in regulation of airway Cl −1 secretion via a Ca 2+ ‐dependent signalling pathway, which involves CaMK and appears to be at least partially conserved in cystic fibrosis airway epithelial cells.