DIRECT EFFECTS OF 2ND-GENERATION H-1-RECEPTOR ANTAGONISTS ON THE ACTIVATION OF HUMAN BASOPHILS

The present study was performed to investigate the putative suppressiv e effects of H-1-receptor antagonists (HRA) of the second generation ( astemizole (AS), cetirizine (CT), loratadine (LO), oxatomide (OX) and terfenadine (TF)) on the mediator release from human basophils activat ed by two classical stimuli. Anti-IgE-mediated histamine release was i nhibited in a dose-dependent fashion by TF (maximum inhibitory value: 33.8 +/- 7.6%, 100 mu M, n = 7), whereas the other HRA exhibited weake r activity. The anti-IgE-induced LTC, production was strongly suppress ed by TF, LO and OX (92.4 +/- 63%, 90.8 +/- 6.0% and 88.5 +/- 5.6%, 10 0 mu M, n = 4-5), while AS was less active (56.4 +/- 4.1%, 100 mu M, n = 5). Histamine release induced by incubation with grass pollen antig en (0.01%) was inhibited by TF (40.7 +/- 4.1%, 50 mu M, n = 4), but th e other HRA showed only low activity. The present findings suggest tha t some HRA might exhibit direct inhibitory effects on activation of Ig E-receptor bearing cells.