ELEVATED CIRCULATING ADENOSINE LEVEL POTENTIATES ANTIGEN-INDUCED IMMEDIATE BRONCHOSPASM AND BRONCHOCONSTRICTOR MEDIATOR RELEASE IN SENSITIZED GUINEA-PIGS

Background: Adenosine causes bronchoconstriction in asthmatic patients , and it is also accepted that adenosine influences histamine release from activated human mast cells and basophils in vitro. Objective: In this study we tested the hypothesis that adenosine potentiates both th e airway narrowing and the release of bronchoconstrictor mediators ind uced by ovalbumin challenge in sensitized guinea pigs. Methods: After ovalbumin sensitization, 4 groups were studied: control group, adenosi ne group (ADO), ovalbumin group (OA), and adenosine plus ovalbumin gro up (ADO + GA). Changes in airway resistance were assessed from continu ously recorded pulmonary insufflation pressure (PIP), The concentratio n of histamine, PGD(2), and thromboxane B-2 were determined from bronc hoalveolar lavage fluids.Results: Adenosine alone (6 mg/kg intravenous ly) did not influence baseline values of PIP and the mediator concentr ations; however, ovalbumin (10 mg/kg intravenously) increased both the PIP and the Levels of the measured mediators compared with the contro l and ADO groups, When ovalbumin challenge was preceded by adenosine a dministration, both PDP and mediator Levels were significantly enhance d compared with values obtained after simple ovalbumin provocation (AD O + OA vs OA: P < .05). Conclusion: These results suggest that adenosi ne potentiates the airway narrowing induced by ovalbumin challenge and that this effect may develop through facilitation of the release of b ronchoconstrictor mediators during the immediate airway response.