Bradykinin-induced burst of prostaglandin formation in osteoblasts is mediated via B2 bradykinin receptors.
The receptor subtype mediating the bradykinin (Bk)-induced burst of prostaglandin formation in osteoblasts has been studied. Bk, but not des-Arg9-Bk, induced the formation of prostaglandin E2 and prostacyclin in neonatal mouse calvarial bones incubated for 30 minutes. Bk-induced prostaglandin synthesis is neonatal mouse calvarial bones was significantly inhibited by the B2 Bk receptor antagonist D-Arg0[Hyp3,Thi5,8,D-Phe7]-Bk. The B2 Bk receptor agonists Bk and Lys-Bk, but not the B1 Bk receptor agonist des-Arg9-Bk, caused a rapid burst (5 minutes) of prostaglandin E2 and prostacyclin formation in isolated osteoblast-like cells from neonatal mouse calvarial bones and in the murine osteoblastic cell lineage MC3T3-E1. When comparing the relative potency of different kinin analogs on their stimulatory effect on prostaglandin formation in isolated osteoblast-like cells and in MC3T3-E1 cells, we found that Bk = Lys-Bk greater than Met-lys-Bk much much greater than Des-Arg9-Bk. Bk-induced prostaglandin synthesis in isolated osteoblast-like cells and in MC3T3-E1 cells was inhibited by D-Arg0[Hyp3,Thi5,8,D-Phe7]-Bk, whereas the B1 Bk receptor antagonist des-Arg9-Leu8-Bk had no effect. Total binding of 3H-Bk (3-20 nM; 4 degrees C) to whole MC3T3-E1 cells reached a maximum after 4-5 h. An excess of nonradioactive Bk (1 microM) reduced cell-associated radioactivity by 20-30%. The B2 Bk receptor agonist Bk and the B2 Bk receptor antagonist D-Arg0[Hyp3,Thi5,8,D-Phe7]-Bk were able to reduce specific binding, but the B1 Bk receptor agonist des-Arg9-Bk was unable to reduce the specific binding of 3H-Bk to whole MC3T3-E1 cells. These findings indicate the presence of B2 Bk receptors on osteoblasts coupled to enhanced prostaglandin synthesis.
Ljunggren
O
O
Department of Oral Pathology, University of Umeå, Sweden.
Vavrek
R
R
Stewart
J M
JM
Lerner
U H
UH
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001920:Bradykinin / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D015232:Dinoprostone / Q000096:biosynthesis* / Q000378:metabolism; D011464:Epoprostenol / Q000096:biosynthesis* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter / Q000737:chemistry / Q000378:metabolism*
D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter; C053748:B 4162; C024626:bradykinin, des-Arg(9)-; D011464:Epoprostenol; D015232:Dinoprostone; D001920:Bradykinin