dihydropyridines and Hypersensitivity

This study investigated the effect of the platelet-activating factor (PAF) receptor antagonist, PCA 4248, on the rat pleurisy caused by PAF, serotonin, bradykinin, histamine or allergen. The pleurisy was assessed by measuring liquid extravasation and leucocyte infiltration. Oral pretreatment with PCA 4248 (2.5-20 mg/kg) completely inhibited the pleural exudation caused by intrathoracic (i.t.) injection of PAF (1 microgram/cavity) (ED50 = 6.1 mg/kg), partially (42% reduction) the one induced by serotonin (100 micrograms/cavity), but was inactive against histamine (200 micrograms/cavity) or bradykinin (50 micrograms/cavity). PCA 4248 blocked the increase in the number of neutrophils, eosinophils and mononuclear cells observed 6 h after the i.t. injection of PAF, as well as the selective eosinophil accumulation noted 24 h later. In actively sensitized rats, PCA 4248 (20 mg/kg) failed to modify the increase in the total leucocyte counts noted 4 h after ovalbumin (12 micrograms/cavity), but dose dependently inhibited the pleural exudation observed within 1 h and the late eosinophil infiltration noted 24 h post-antigen. These observations led us to suggest that PCA 4248 is a potent PAF antagonist with anti-serotoninergic properties. Its interference with exudation and eosinophil infiltration caused by allergen is consistent with the interpretation that PCA 4248 may be useful in the management of allergic dysfunctions.

Topics: Allergens; Animals; Bradykinin; Dihydropyridines; Edema; Eosinophils; Exudates and Transudates; Female; Histamine; Hypersensitivity; Leukocyte Count; Male; Neutrophils; Platelet Activating Factor; Platelet Membrane Glycoproteins; Pleurisy; Rats; Rats, Wistar; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Serotonin

A new series of oxopyridinecarboxamide derivatives 3a--g and 5a were synthesized and evaluated for their antiallergic activity. 1,4-Dihydro-7-methyl-4-oxo-1,8-naphthyridine-3-carboxamides 3a and 5a exhibited potent antiallergic activity (inhibitory rates of 80.7 and 88.3%, respectively, at 20 mg/kg, p.o.) in the rat passive cutaneous anaphylaxis (PCA) test and also exhibited much more potent in vitro inhibitory activity than caffeic acid against the enzyme 5-lipoxygenase (5-LO). Their in vitro antihistamine activity, however, was weaker than that of ketotifen. Compounds 3a and 5a are viewed as promising candidates for antiallergic agents.

Topics: Animals; Chemical Phenomena; Chemistry; Dihydropyridines; Histamine Release; Hypersensitivity; Lipoxygenase Inhibitors; Male; Passive Cutaneous Anaphylaxis; Piperazines; Rats; Rats, Inbred Strains