Identification of [³H] histamine binding sites on gastric mucosal cells unrelated to histamine H₂-receptors

Binding of ³H-histamine to guinea pig gastric mucosal cells was inhibited by various imidazole and indole derivatives as well as by histamine and its H₂-receptor agonists and antagonists. In contrast to the H₂-agonists or H₂-antagonists, these derivatives (e.g. imidazole, 4-hydroxymethyl imidazole, tryptamine, serotonin), neither increased cellular cyclic AMP nor altered the increase in cyclic AMP caused by histamine. The imidazole derivatives were more potent in inhibiting [³H]histamine binding than the corresponding indole derivatives. These results confirm our earlier observations suggesting that gastric cells posses a class of binding sites for ³H-histamine that is not linked to adenylate cyclase and is unrelated to the histamine H₂-receptor.