CROSSTALK - PHOSPHORYLATION ALPHA(1B)-ADRENOCEPTORS INDUCED THROUGH ACTIVATION OF BRADYKININ B2 RECEPTORS

The action of bradykinin was studied in rat-1 fibroblasts stably expre ssing alpha(1b)-adrenoceptors. It was observed that bradykinin and kal lidin markedly increase cytosol calcium concentration, but that the B1 agonist, des-Arg(9)-bradykinin only mimicked this effect to a minimal extent. Antagonists, selective for the B2 subtype, such as Hoe 140, b locked this effect of bradykinin and kallidin. Similarly, bradykinin a nd kallidin stimulated the production of inositol phosphates and B2 an tagonists blocked their actions. The possibility that bradykinin could modulate alpha(1b)-adrenoceptors was studied. It was observed that br adykinin and kallidin increased alpha(1b)-adrenoceptor phosphorylation and that such effect was also blocked by Hoe 140. Interestingly, the ability of norepinephrine to increase intracellular calcium concentrat ion was not altered by pretreatment of the cells with bradykinin, i.e. bradykinin induced alb-adrenoceptor phosphorylation but this did not lead to receptor desensitization. (C) 1998 Federation of European Bioc hemical Societies.