[Effects of methylflavonolamine hydrochloride on tension and cAMP of isolated guinea pig trachea].

Effects of methylflavonolamine (4'-methyl-7-(2-hydroxy-3-isopropylaminopropoxy)-flavone hydrochloride, MFA) on the tension and cAMP content of isolated guinea pig tracheal smooth muscle strips were studied. MFA (0.03-0.6 mmol.L-1) dose-dependently reduced KCl, acetylcholine (ACh) and histamine (Hist)-induced contractions with intracellular increase in cyclic AMP. The reduction in contraction and increase in cAMP were well correlated positively. MFA (0.03 mmol.L-1) showed synergism with isoprenaline (Iso) and aminophylline (Ami) in bronchodilation. The synergism with Iso but not Ami was accompanied by an increase in cAMP levels. It is suggested that the MFA-induced bronchodilation is related to the increase in intracellular cAMP level. The calcium antagonistic effect may be involved in MFA-induced bronchodilation.