Correlation between cholinergic histamine release and quinuclidinyl-benzilate ([3H]-QNB) binding in mast cell membranes

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Abstract
Isolated purified rat mast cells release histamine when exposed to acetylcholine according to a different pattern of sensitivity. No correlation was found between the release of histamine evoked by acetylcholine and the high affinity binding of [3H]-quinuclidinyl-benzilate (QNB), a specific cholinergic muscarinic ligand, to rat mast cell membranes, since QNB binding was the same in membrane isolated from cells which were sensitive or insensitive to acetylcholine. In murine neoplastic mast cells, a negative correlation was found between histamine release and [3H]-QNB binding, as no evidence of specific [3H]-QNB binding was present in murine neoplastic mast cell membranes which, accordingly, do not release histamine when exposed to acetylcholine. It is concluded that murine neoplastic mast cells are not provided with muscarinic cholinergic receptors. In rat mast cells, muscarinic cholinergic receptors are always present, but not always coupled with the effector mechanisms triggering the exocytosis.