Haptoglobin-stimulated bone resorption in neonatal mouse calvarial bones in vitro.
OBJECTIVE
To study the in vitro effects of human haptoglobin (Hp) on bone resorption and prostanoid formation.


METHODS
Parietal bones were dissected out from neonatal mice that had been injected with 45Ca, and were cultured in chemically defined medium with or without test substances. Bone resorption was assessed by analysis of 45Ca release. Prostanoid formation was quantified by analysis of the amount of prostaglandin E2 (PGE2) in culture medium.


RESULTS
Hp phenotype 2-1, in quantities greater than or equal to 0.17 mg/ml, stimulated the release of 45Ca and the biosynthesis of PGE2, in a time- and dose-dependent manner. Hp-induced PGE2 formation was abolished by indomethacin and flurbiprofen, whereas the stimulation of 45Ca release was only partially reduced.


CONCLUSIONS
These observations suggest that the acute-phase reactant Hp may contribute, by a humoral mechanism, to the bone resorption seen in chronic inflammatory processes.
Lerner
U H
UH
Department of Oral Cell Biology, University of Umeå, Sweden.
Fröhlander
N
N
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001172:Arthritis, Rheumatoid / Q000503:physiopathology; D001862:Bone Resorption / Q000139:chemically induced*; D001842:Bone and Bones / Q000378:metabolism / Q000502:physiology*; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D006242:Haptoglobins / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D010019:Osteomyelitis / Q000503:physiopathology; D010518:Periodontitis / Q000503:physiopathology; D012886:Skull
D006242:Haptoglobins; D001920:Bradykinin; D002118:Calcium