title: Differential effects of fluoride during initiation and progression of mineralization of osteoid nodules formed in vitro.
abstract: Osteoid nodules form in cultures of fetal rat calvarial (RC) cells grown in medium containing 10% FBS and 50 micrograms/ml of ascorbic acid. When 10 mM beta-glycerophosphate (beta-GP) is added, osteoid nodules mineralize in two phases: an initiation phase, which is dependent upon alkaline phosphatase activity for conversion of beta-GP to P(i), and a progression phase that proceeds independently of alkaline phosphatase activity and does not require exogenous phosphate. We have now used this system to investigate the effects of fluoride (F-) on mineralization. In cultures in which osteoid was formed and mineralization initiated in the presence of F-, a dose-dependent inhibition of the initiation of mineralization occurred over a concentration range of 25-500 microM F- (p < 0.001 in all cases). The initiation of mineralization was not inhibited if F- was removed from the cultures at the time when mineralization was initiated with beta-GP. In osteoid nodules grown in the absence of F-, addition of F- resulted in a dose-dependent inhibition of the initiation of mineralization, with significant decreases in 45Ca uptake occurring at F- concentrations of 3 microM (p < 0.01) and higher. However, if F- was added to cultures after mineralization was initiated in the absence of F-, a stimulation of 45Ca uptake was observed at F- concentrations of 250 microM and above (p < 0.001). F- (1-1000 microM) did not affect the conversion of beta-GP to P(i) or alkaline phosphatase activity in the cultures.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: MRC Group in Periodontal Physiology, Faculty of Dentistry, University of Toronto, Ontario, Canada.
authors.forename: C G
authors.initials: CG
authors.lastname: Bellows
authors.forename: J E
authors.initials: JE
authors.lastname: Aubin
authors.forename: J N
authors.initials: JN
authors.lastname: Heersche
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002113:Calcification, Physiologic / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005459:Fluorides / Q000494:pharmacology*; D010012:Osteogenesis / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012886:Skull / Q000166:cytology / Q000187:drug effects; D013997:Time Factors
chemical_list: D000469:Alkaline Phosphatase; D005459:Fluorides; D002118:Calcium