The effect of bradykinin on the activation production of inositol 1,4,5-triphosphate and prostaglandin E2(PGE2) was examined in the murine osteoblastic cell line, MC3T3-E1. Bradykinin, at concentrations ranging from 1 to 1000 nM, stimulated the production of inositol 1,4,5-triphosphate 2.5- to 3-fold within 10 s, and elevated cytosolic-free Ca2+, even in the absence of external Ca2+. This process is mediated through the activation of phospholipase C. Bradykinin at the same concentration also stimulated the production of PGE2 and caused a release of 3H radioactivity of the cells prelabeled with [3H]arachidonic acid, probably via the activation of phospholipase A2. Pretreatment of the cells with pertussis toxin inhibited the stimulation of PGE2 production and 3H radioactivity release, while the elevation in cytosolic Ca2+ and the production of inositol 1,4,5-triphosphate were not altered by toxin-pretreatment. The addition of an unhydrolyzable analog of GTP, guanosine 5′-[γ-thio]triphosphate (GTPγS) to the β-escin-permeabilized cells prelabeled with [3H]arachidonic acid enhanced the release of 3H radioactivity. The simultaneous presence of bradykinin with GTPγS further activated the 3H radioactivity release in the β-escin-permeabilized cells. These results provide evidence that receptors for bradykinin in the MC3T3-E1 couple, stimulating arachidonate release, probably via the activation of phospholipase A2, through a guanine nucleotide binding protein sensitive to pertussis toxin.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology