Inhibition of antigen-induced histamine release by beta-adrenergic stimulants in vivo.

IgE-mediated histamine release was studied using the method of passive peritoneal anaphylaxis (PPA) in the rat. Some beta-adrenergic stimulants markedly inhibited this reaction in vivo, the order of potency (ED50 microng/kg i.v.) of agents tested being fenoterol (6), salbutamol (40) and isoproterenol (94). Higher activity against the simultaneously measured dye extravasation suggested a dual effect of the drugs on both the cellular (inhibition of histamine release) and the vascular level. The order of potency in modifying vascular injury was, however, reversed, isoproterenol and not fenoterol being relatively more active here, as could be shown by further experiments. Inhibition of histamine release is discussed with respect to (a) methodical requirements and (b) the suggestion that beta2-receptor stimulants (fenoterol, salbutamol) are more selective than isoproterenol.