Effect of fluoride on molecular size of proteoglycans in the rat incisor tooth

Odontoblast transport of sulphate--the in vitro influence of fluoride

The present study reports the development of a culture system for the analysis of 35S-sulphate release from odontoblasts in vitro. Pulpless longitudinally split rat incisors were cultured in supplemented minimum essential medium (alphaMEM) with 20 microCi 35S-sulphate per ml, 20 microCi 3H-mannitol per ml for 1h. Teeth were then transferred to fresh unlabelled media and aliquots of media were removed and the level of 35S-sulphate 3H-mannitol determined. Results indicated a two phase release of 35S-sulphate into the media, and comparison with pulp tissue indicated a specific release pattern. Transport of sulphate is essential for correct synthesis and glycosylation of macromolecules such as proteoglycans (PG). Previous studies have shown that post-translational modifications of these proteins can be influenced by excess fluoride, resulting in decreased sulphation and elongation of glycosaminoglycan (GAG) chains. Therefore the influence of fluoride on sulphate transport, using the optimised culture system was also investigated. Inclusion of 6mM fluoride during pulse labelling caused a significant decrease of 35S-sulphate (P<0.0001) during the initial release phase. Inclusion of 3 and 6mM fluoride only in the post-labelling incubation media resulted in a significant decrease in the release of 35S-sulphate (P<0.0001), during the total time course. The influence of fluoride was not dose dependent. Inclusion of a specific chloride channel blocker SITS, into the culture system indicated that 35S-sulphate transport may in part be via this route. Fluoride would therefore appear to influence the transport of 35S-sulphate across the odontoblast membrane, potentially via a chloride channel.

Modification of the proteoglycans of rat incisor dentin-predentin during in vivo fluorosis

Proteoglycans (PGs) were isolated from the dentin-predentin of fluorotic and control rat incisor teeth using demineralization in EDTA, followed by extraction with 4 M guanidinium chloride in the presence of protease inhibitors. Differences in the behaviour of fluorotic and control PG were evident during purification by anion exchange chromatography on Q-Sepharose and MONO-Q interfaced with fast protein liquid chromatography. The PG from fluorotic teeth exhibited a more anionic profile, due to changes in glycosaminoglycan characteristics, since no apparent differences were evident between the respective core proteins, both of which were 45 kDa. The constituent glycosaminoglycan chains of fluorotic dentin were of lower molecular size and showed the additional presence of dermatan sulfate and heparan sulfate by comparison to nonfluorotic controls, where only chondroitin-4-sulfate was detected.

The effect of vitamin A deficiency and fluoride on glycosaminoglycan metabolism in bone

The effects of fluoride intake and vitamin A deficiency on glycosaminoglycan metabolism in vivo were investigated. Weanling female rats were fed either a vitamin A deficient diet ad libitum, a vitamin A supplemented diet pair-fed to the deficient animals, or the vitamin A supplemented diet ad libitum. Additionally, each vitamin A dietary group was divided into three subgroups with the animals receiving water containing 0, 10 or 50 ppm fluoride. The results showed that the groups receiving 10 and 50 ppm fluoride at all dietary levels of vitamin A had significantly higher in vivo 35SO4 incorporation in both the epiphyseal and diaphyseal regions of the bone than the animals receiving 0 ppm fluoride. The vitamin A deficient animals incorporated significantly less 35SO4 into glycosaminoglycans in the epiphyseal and diaphyseal regions of the bone compared to the pair-fed, vitamin A sufficient animals for all three fluoride receiving groups. There was no interaction between fluoride intake and dietary vitamin A levels on 35SO4 incorporation into glycosaminoglycans. Fluoride either increased sulfation or turnover of glycosaminoglycans.

Electron microscopic visualization of proteoglycans in rat incisor predentine and dentine with cuprolinic blue

Cuprolinic blue in a MgCl2-critical electrolyte concentration solution allows a larger surface representation of proteoglycans than other methods. Glycoaminoglycans in predentine were ribbon-like structures 14 nm thick and 60 nm long, with radiating filaments (3-4 nm) located in spaces between collagen fibres. Glycoaminoglycans and collagen together displayed longitudinal and orthogonal relationships. The ground substance was slightly electron dense. In dentine, the precipitate was less in quantity and consisted of rounded granules (15 nm in diameter, and filaments/3 nm in width) closely associated with the surfaces of collagen fibres.

The influence of fluoride administration on the structure of proteoglycans in the developing rat incisor

1. 35S-labelled chondroitin 4-sulphate proteoglycan was isolated from the mineralized elements of the developing incisor teeth of Harvard rats receiving intraperitoneal administration of Na235SO4. 2. The chondroitin 4-sulphate proteoglycan underwent a decrease in molecular size in fluorotic teeth as judged by gel filtration on Sepharose 2B. 3. When examined by anion-exchange chromatography on DEAE cellulose-52, the proteoglycan from fluorotic teeth resolved into four peaks in comparison with the material from non-fluorotic teeth, which exhibited only a single major peak. 4. Both the single peak from non-fluoridated teeth and the four peaks from the fluorotic teeth were further resolved on cellulose acetate electrophoresis. 5. Isolated chondroitin 4-sulphate chains obtained from fluorotic teeth also were of smaller molecular size as judged by gel filtration on Sephadex G-150. 6. Some possible influences of fluoride on the metabolism of these connective-tissue components in the developing rat incisor are discussed.

A microspectrophotometric analysis of the effect of fluoride on immature enamel matrix protein of rat molar teeth

Over a 24-h period, Wistar rats from 4 litters, 6 to 9 days old, were given five intraperitoneal injections of a solution of 0.9% sodium chloride containing sodium fluoride (3 mg F/kg body weight). Within-litter controls were used. All rats were killed by decapitation 2 h after the final injection and the rat heads, cut sagittally, were processed for protein histochemistry. The intensity of staining of the protein in the enamel matrix of the upper jaw molar tooth buds was quantified using the two-wavelength method of microphotometry. A significant increase in the intensity of staining of fluoride-treated tissues over controls was observed with the histochemical methods specific for arginine (P less than 0.01), tyrosine (P less than 0.05), and cysteine (P less than 0.05). Other histochemical methods specific for amino acid groups failed to show any significant difference between fluoride and non-fluoride-treated enamel matrix.