| Abstrakt: |
Bovine aortic and cerebral microvascular endothelial cells and cultured segments of canine common carotid artery possess functional receptors for the nonapeptide bradykinin which mediate a rapid increase in the formation of [3H]inositol 1-phosphate, [3H]inositol 1,4-bisphosphate, and [3H]inositol 1,4,5-trisphosphate from cell membranes containing isotopically labeled myo-inositol. Bradykinin stimulated the formation of [3H]inositol phosphates from cells in culture or tissues at threshold concentrations of 0.1 nM and 1 nM, and with a half-maximal effective concentration of 0.6-1.0 nM and 30 nM, respectively. In cultured cells, the formation of [3H]inositol trisphosphate and [3H]inositol bisphosphate preceded the formation of [3H]inositol monophosphate. Similarly, [3H]inositol phosphate formation was not inhibited by addition of calcium channel blockers, a calcium chelator, or an intracellular calcium antagonist. Calcium ionophore A23187 did not promote [3H]inositol phosphate accumulation. The receptor selectivity of the bradykinin response in cultured cells was most compatible with a type-2 mediated response. Kallidin stimulated with the same potency as bradykinin but was more potent than methionyl-lysyl-bradykinin or des-Arg9-bradykinin. The B1 receptor antagonists des-Arg9-[Leu8]-bradykinin and des-Arg10-[Leu9]-kallidin were without effect. The rapidity of the inositol phosphate response as well as the close correspondence between the bradykinin type-2 receptor mediated hydrolysis of polyphosphoinositides and changes in prostacyclin synthesis, vessel dilation, and permeability suggests that breakdown products of inositol lipids serve as second messengers mediating the effects of bradykinin on the vascular endothelium. |
