Relaxant effect of trapidil on isolated dog bronchus.
Relaxant effects of trapidil on dog bronchi were pharmacologically analyzed in vitro. Trapidil concentration-dependently relaxed bronchial strips contracted with methacholine, histamine or potassium. In the strips under methacholine-contracture, theophylline, papaverine, isoproterenol and atropine produced concentration-dependent relaxations. Propranolol significantly decreased isoproterenol-induced relaxations of bronchial strips under methacholine-contracture, but did not trapidil-induced relaxations. Prostaglandin (PG) E1 and PGE2 in high doses slightly relaxed bronchial strips under methacholine-contracture, but PGI2 hardly affected them. Tranylcypromine did not influence relaxant responses of the strips to trapidil. The results indicate that trapidil produces relaxations of bronchial smooth muscle through a non-specific action other than adrenergic beta-receptor activation or endogenous prostaglandin biosynthesis.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001980:Bronchi / Q000187:drug effects; D001993:Bronchodilator Agents; D004285:Dogs; D005260:Female; D008297:Male; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D011743:Pyrimidines / Q000494:pharmacology*; D014191:Tranylcypromine / Q000494:pharmacology; D014192:Trapidil / Q000494:pharmacology*
D001993:Bronchodilator Agents; D008688:Methacholine Compounds; D011743:Pyrimidines; D016210:Methacholine Chloride; D014191:Tranylcypromine; D001285:Atropine; D014192:Trapidil