Evaluation of novel compounds interacting with H2-histamine receptors: effect on histamine-sensitive adenylate cyclase activity in guinea-pig gastric mucosa

The activity of a number of compounds belonging to the novel class of N-imidazolylphenyl-N'-alkyl-formamidines on histamine-sensitive Adenylate Cyclase was evaluated. All substances inhibited histamine-dependent Adenylate Cyclase activation. The compounds which were investigated in a wider concentration range, i.e. DA 4360, DA 4577, and DA 4626, behaved as simple competitive antagonists, yielding apparent KB values comparable with those estimated in conventional H2-receptor assays. These results provide further evidence for the highly selective H2-receptor antagonism of these new molecules, and confirm the suitability of the histamine-stimulated Adenylate Cyclase assay in guinea-pig gastric cells as a functionally reduced system for the study of H2 antagonists.