title: Potent bronchodilating effects of enprofylline and theophylline on contractions induced by egg albumin or by slow reacting substance (SRS).
abstract: Isolated sensitized guinea pig tracheal smooth muscle tone was induced by use of egg albumin or SRS-A (slow reacting substance of anaphylaxis). The dose-response relationships of theophylline and enprofylline were studied on these preparations. Enprofylline was more potent than theophylline in relaxing the egg albumin- or SRS-A-induced tracheal muscle tone. The theophylline relaxation-curve was significantly shifted to the left after addition of adenosine-deaminase to the egg albumin-contracted trachea, but this was not observed with the enprofylline relaxation-curve. In SRS-A-contracted tracheas, the addition of adenosine-deaminase did not significantly alter the relaxation curves of theophylline or enprofylline. It is therefore suggested that the relaxing effects of theophylline and enprofylline on SRS-A-induced contractions, at the therapeutically relevant concentrations demonstrated in this study, might be of importance for the anti-asthmatic effects of xanthines.
mesh_terms: D000243:Adenosine Deaminase / Q000494:pharmacology; D000418:Albumins / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D000818:Animals; D001980:Bronchi / Q000187:drug effects*; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D013189:SRS-A / Q000494:pharmacology; D013806:Theophylline / Q000494:pharmacology*; D014132:Trachea; D014970:Xanthines / Q000494:pharmacology*
chemical_list: D000418:Albumins; D013189:SRS-A; D014970:Xanthines; D013806:Theophylline; C034347:enprofylline; D000243:Adenosine Deaminase