The anti-allergic effect of 2, 4-bis (2'-acetoxybenzamido)-benzoic acid (AB-50), newly synthesized in this laboratory, were examined. AB-50 inhibited IgE-mediated passive cutaneous anaphylaxis (PCA) in rats. When administered orally 30 minutes before antigenic challenge, dose-dependent inhibition was observed over a range of doses of 100-1000mg/kg. Direct intraduodenum administration was far much effective, i.e., marked inhibition was shown at a dose of 20mg/kg, although intrastomach administration of 100mg/kg was not so effective. Maximum inhibition was obtained when administered 30 minutes before challenge by both oral and intraduodenum routes of administration. AB-50, administered intravenously or orally before challenge, also suppressed IgG-mediated PCA in guinea-pigs, however, disodium cromoglycate (DSCG) was inactive in this experimental model. Systemic anaphylactic shock of rats or guinea-pigs were prevented by intravenous injection of AB-50 in a dose of 10-40mg/kg. AB-50 did not have an antagonistic effect against chemical mediators of the IgE-mediated PCA such as histamine, serotonin and bradykinin, nor did it have an anti-inflammatory activity. These results and inhibitory activity of anaphylactic histamine release from mast cells as previously reported suggested that mode of action for AB-50 is similar to DSCG. However, AB-50 has two advantages as follows: 1)Oral adminstration is effective; 2)It could inhibit IgG-mediated anaphylactic reaction.
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