Role of protein kinase C in bradykinin-induced prostaglandin formation in osteoblasts.

UNLABELLED

Bradykinin (1 microM, 5 min) induced translocation of protein kinase C (PKC) to the plasma membrane fraction in osteoblastic MC3T3-E1 cells. Bradykinin also enhanced the binding of phorbol 12,13-dibutyrate (PDBu) to intact cells, a measure of PKC activation. Addition of bradykinin (1 microM) to cells preincubated with [3H]PDBu (10 nM, 20 min) caused an increase in specific PDBu binding that was maximal after 5-10 min. The bradykinin-induced enhancement of PDBu binding was seen at 1 nM and was maximal at 10 nM. The bradykinin B1 receptor agonist des-Arg9-bradykinin (1 microM) did not enhance specific PDBu binding to intact MC3T3-E1 cells. PDBu at and above 3 nM stimulated the formation of prostaglandin E2 (PGE2) in MC3T3-EI cells. This stimulatory effect was seen after 15-20 min incubation. The Ca2+ ionophore A23187 at and above 1 microM induced a rapid (within seconds) burst of PGE2 formation in MC3T3-E1 cells. The effect of PDBu and A23187 on PGE2 formation was synergistic. The PKC inhibitor staurosporine (200 nM) inhibited basal as well as bradykinin-induced prostaglandin-formation in MC3T3-E1 cells.

IN CONCLUSION

bradykinin enhances PKC activation in osteoblastic MC3T3-E1 cells. This kinase activation may be involved in bradykinin-induced prostaglandin formation.