Inhibition of Antigen-Induced Contraction of Guinea Pig Isolated Tracheal Muscle with 2-n-butyl-3-dimethylamino-5,6-methylenedioxy indene (MDI-A), indane (MDI-B) and 8-(diethylamino)octyl-3,4,5-trimethoxy benzoate hydrochloride (TMB-8)

Abstract

The effects of three intracellular calcium antagonists on antigen-induced contraction of sensitized guinea pig tracheal muscle were investigated. The agents employed were: 2-n-butyl-3-dimethylamino-5,6-methylenedioxy indene hydrochloride (MDI-A), 2-n-butyl-3-dimethylamino-5,6-methylenedioxy indane hydrochloride (MDI-B) and 8-(diethylamino)octyl-3,4,5-trimethoxy benzoate hydrochloride (TMB-8). Each of these agents caused a concentration-dependent inhibition of the antigen-induced contraction of sensitized tracheal smooth muscle. Moreover, in histamine and leukotriene D4 (LTD4) incited contractions of guinea pig tracheal muscle, they showed antagonistic action. The induced tracheal muscle contraction, achieved through the addition of compound 48/80 to a solution of ethylene glycol bis (beta-aminoethylether)-N,N,N1, N1-tetraacetic acid (EGTA) in a contained Ca-free medium, was completely inhibited by individual pretreatment with MDI-A, MDI-B and TMB-8. In the case of tracheal muscle contraction induced by CaCl2 in a high potassium, Ca-free medium, only TMB-8 inhibited contraction. Lastly, none of these three intracellular calcium antagonists affected the antigen-induced release of histamine and slow reacting substance of anaphylaxis (SRS-A). These results suggest that MDI-A and MDI-B inhibit the antigen-induced contraction of sensitized guinea pig tracheal muscle by interfering with the contractile responses caused by histamine and LTD4.