Theophylline's inhibition of antigen-induced contraction of human parenchymal strips is independent of adenosine antagonism.
The effects of theophylline, and adenosine antagonist, and enprofylline, reported to lack adenosine antagonism, were studied using antigen-induced contraction of sensitized human lung parenchymal strips. Cumulative addition of adenosine usually resulted in a small concentration-dependent contraction, which was antagonized by theophylline, 100 microM. Antigen-induced contraction was reduced by pretreatment with adenosine, 10 microM, but not by adenosine addition after antigen challenge. Dipyridamole, 2 microM, pretreatment did not change adenosine's effect. Theophylline, 100 microM, caused relaxation of the lung strips and reduced their response to antigen. It did not affect the response to adenosine. Enprofylline, 100 microM, caused a relaxation of parenchyma greater than that of theophylline. It reduced the contractile response to antigen and potentiated the reduction caused by adenosine. Thus, neither drug antagonized the effect of adenosine on antigen-induced contraction. Antigen-induced histamine release from the lung parenchymal strip was not modified by any of these drugs.
D000241:Adenosine / Q000037:antagonists & inhibitors*; D000403:Airway Resistance / Q000187:drug effects*; D000941:Antigens; D001993:Bronchodilator Agents / Q000494:pharmacology; D006636:Histamine Release / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects; D012130:Respiratory Hypersensitivity / Q000503:physiopathology*; D013806:Theophylline / Q000494:pharmacology*; D014970:Xanthines / Q000494:pharmacology
D000941:Antigens; D001993:Bronchodilator Agents; D014970:Xanthines; D013806:Theophylline; C034347:enprofylline; D000241:Adenosine