Regulation by monovalent cations of histamine H2 receptor-coupled adenylate cyclase from guinea pig fundic gastric mucosa.

In thoroughly washed guinea pig fundic gastric mucosal membranes, NaCl markedly potentiates the maximal histamine-stimulated adenylate cyclase activity and increases the concentration of histamine required for half-maximal effect (EC50). The apparent dissociation constants for the antagonists cimetidine and metiamide are only slightly increased in the presence of NaCl. Potassium chloride does not change the histamine EC50 but does increase the maximal histamine-stimulated adenylate cyclase activity. These results suggest that Na and K ions may play an important role in the regulation of histamine-sensitive adenylate cyclase in gastric mucosa. The effect of the Na ion appears to be more specific for histamine H2 receptor agonists than for antagonists.