Affiliation:
1. Department of Pharmacology, School of Medicine, East Carolina University, Greenville, North Carolina 27858
Abstract
The signal transduction pathway for A1 adenosine receptor in airway smooth muscle from allergic rabbits was studied by investigating the effect of the selective A1adenosine-receptor agonist N 6-cyclopentyladenosine (CPA) on tissue levels of inositol 1,4,5-trisphosphate [Ins(1,4,5) P 3] measured by protein binding assay. CPA caused a rapid, transient, and concentration-dependent elevation of Ins(1,4,5) P 3 in airways from allergic rabbits. The agonist also produced a concentration-dependent contraction of the airway preparations from these animals. Both the Ins(1,4,5) P 3 and contractile responses generated by CPA were attenuated by the phospholipase C (PLC) inhibitor U-73122, indicating the coupling of these responses to PLC. The CPA-induced Ins(1,4,5) P 3production observed in the allergic rabbit tissues was also inhibited by the adenosine-receptor antagonist 8-( p-sulfophenyl)-theophylline, suggesting that the effect was mediated by A1 adenosine receptors. On the other hand, the A2adenosine-receptor agonist CGS-21680 was ineffective in altering the tissue concentration of Ins(1,4,5) P 3, indicating that A2 adenosine receptors may not be involved in the activation of PLC in the allergic rabbit airway smooth muscle. In this preparation, the Gi-Goinhibitor pertussis toxin (PTX) attenuated the CPA-induced Ins(1,4,5) P 3accumulation, providing evidence that the generation of Ins(1,4,5) P 3 by A1 adenosine-receptor stimulation is coupled to a PTX-sensitive G protein(s). The results suggest that activation of A1 adenosine receptors in allergic rabbit airway smooth muscle causes the production of Ins(1,4,5) P 3via a PTX-sensitive G protein-coupled PLC, and this signaling mechanism may be involved, at least in part, in the generation of contractile responses. It is hypothesized that this process may contribute to adenosine-induced bronchoconstriction in allergic asthma.
Publisher
American Physiological Society
Subject
Cell Biology,Physiology (medical),Pulmonary and Respiratory Medicine,Physiology
Cited by
42 articles.
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