Studies on the anti-allergic action of N-(3',4'-dimethoxycinnamoyl) anthranilic acid (N-5')

The effects of the anti-allergic compound (N-(3',4'-dimethoxycinnamoyl) anthranilic acid (N-5' or Tranilast) have been investigated upon antigen-induced contractions of respiratory smooth muscle in vitro and bronchoconstriction in vivo. N-5' (3.1 X 10(-5) M) in vitro had no significant effect upon antigen-induced contractions of the guinea pig trachea. However, when tested at concentrations of 9.2 and 3.1 X 10(-5) M, but not 0.9 X 10(-5), N-5' significantly inhibited antigen-induced contractions of the human parenchyma. In vivo N-5' (5 and 10 mg/kg p.o.) failed to inhibit antigen-induced dyspnea in hyperreactive rats. N-5' (20 mg/kg p.o.) also failed to inhibit the immediate bronchoconstriction following ascaris challenge of conscious squirrel monkeys but significantly attenuated the reduction in dynamic compliance during the pulmonary late phase response observed between 4 and 10 h after antigen challenge. It is suggested that N-5' does not act as a "cromoglycate-like" compound but may have novel mechanisms of action in human bronchial asthma.