Rj. Waddington et al., THE INFLUENCE OF FLUORIDE ON PROTEOGLYCAN STRUCTURE USING A RAT ODONTOBLAST INVITRO SYSTEM, Calcified tissue international, 52(5), 1993, pp. 392-398
Using an in vitro rat incisor odontoblast system, the effect of fluori
de on proteoglycans was investigated at both the metabolic and structu
ral level. Incisors were removed from 4-week-old rats, split longitudi
nally, and the pulps removed. Teeth were incubated at 37-degrees-C, 5%
CO2 in Eagle's Minimum Essential Medium containing S-35-sulfate for 7
hours in the presence of 0 mM, 3 mM, or 6 mM sodium fluoride. Teeth w
ere demineralized in EDTA, proteoglycan was extracted from the residue
with 4 M guanidinium chloride, and further purified by anion exchange
chromatography. Uptake of radiolabel was monitored by liquid scintill
ation counting. The resultant products were examined by cellulose acet
ate electrophoresis, SDS-PAGE, chondroitinase digestion, and amino aci
d analysis. Differential effects of fluoride were observed in both met
abolism and biochemical characterization of proteoglycans following in
cubation at the two concentrations. Fluoride decreased uptake of the r
adiolabel but led to an accumulation of glycosaminoglycan within the p
roteoglycan of the matrix. Chondroitin sulfate was the predominant gly
cosaminoglycan identified, with the additional presence of dermatan su
lfate and heparan sulfate identified. Dermatan sulfate levels increase
d in 3 mM-treated teeth. Fluoride-treated proteoglycans had a reduced
molecular weight (200-90K to 180-79K), this reduction is primarily a r
esult of smaller glycosaminoglycan chains, with limited reduction in t
he size of the core protein of 6 mM-treated teeth occurring. Such alte
rations in the biochemical metabolism and hence structure and function
of proteoglycan may be implicated in the hypomineralization seen in f
luorosis.