THE INFLUENCE OF FLUORIDE ON PROTEOGLYCAN STRUCTURE USING A RAT ODONTOBLAST INVITRO SYSTEM

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.