Bradykinin action in the rat duodenum: receptor binding and influence on the cyclic AMP system.

Bradykinin binds to a single class of binding sites at rat duodenum plasma membranes. In the presence of endogenous calcium and at low bradykinin concentrations the receptor activation is followed by a stimulation of adenylate cyclase activity and the elevation of the cAMP level. In the absence of calcium and at high peptide concentrations the cAMP level is lowered via both inhibition of adenylate cyclase and stimulation of cAMP-phosphodiesterase. These different changes in the cAMP level might be correlated with the biphasic pharmacological action of bradykinin in the rat duodenum. The results suggest that one type of bradykinin (B2) receptor is able to initiate several effectuation mechanisms.