Presence of functionally active beta-adrenoceptors in rat mast cells. Correlation between (--)[3H]-dihydroalprenolol binding and inhibition of histamine release.

The correlation between the binding of a beta-adrenoceptor antagonist, (--)[3H]-dihydroalprenolol (DHAP), and the adrenergic inhibition of histamine release by acetylcholine and by compound 48/80 was studied with isolated purified rat mast cells and in rat mast cell crude membrane fractions. Acetylcholine-evoked histamine release was inhibited by catecholamines, in the order isoprenaline greater than adrenaline greater than noradrenaline. Pretreatment of cells with (--)alprenolol antagonized the inhibitory effect of isoprenaline on acetylcholine-induced histamine release. 40/80-evoked histamine release was blocked by isoprenaline at significantly higher concentrations than those required to inhibit cholinergic histamine release. The inhibitory effect of isoprenaline was equally antagonized by preincubating mast cells with (--)alprenolol. Specific binding sites for DHAP have been demonstrated in rat mast cell membranes. The specific binding of DHAP was inhibited by adrenoceptor agonists and antagonists according to the stereospecificity of these compounds. A close correlation between the binding-inhibitory potency of various adrenergic compounds and the data obtained in the pharmacological experiments was found, thus indicating the presence of beta-adrenoceptors in rat mast cells.