Effects of fluoride on glycosaminoglycan of cancellous and cortical bone of rabbits

Changes in serum seromucoid following compensatory hyperparathyroidism: A sequel to chronic fluoride ingestion

This study was conducted to find out the possible underlying mechanism of various manifestation of fluorosis, a disease caused by excess ingestion of fluoride. For this the fluoride belt of Jaipur district was selected. The parameters selected were serum Parathyroid hormone, the levels of which are directly affected by fluoride intake. The levels of serum seromucoid, serum and leucocyte ascorbic acid, serum sialic acid (SSA) reflects ground substance metabolism. The study was conducted on two hundred children, selected from four areas (50 from each area) consuming water containing 2.4, 4.6, 5.6 and 13.6 mg/l of fluoride. Drinking water fluoride and serum fluoride were measured by Ion selective electrode method. Serum parathyroid by RIA and all other parameters were measured spectrophotometrically. The results revealed an increase in levels of fluoride, parathyroid hormone and seromucoid in serum with increasing water fluoride concentrations. Serum Calcium and serum ascorbic acid were found in normal range, how ever leucocyte ascorbic acid were decreased. A high positive correlation among fluoride concentration in drinking water and serum parathyroid hormone (r=0.967), and, serum parathyroid hormone and serum seromucoid concentration (r=0.935) was also observed The results indicated that secondary hyperparathyroidism due to hypocalcemic stress caused by excess fluoride ingestion disturbs normal metabolism of ground substance in calcified tissues of the body reflected as altered levels of the components of ground substance in the serum.

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.

Bone effects of fluoride in animal models in vivo. A review and a recent study

The effects of fluoride on bone in various animal models are reviewed. In these studies, the doses of fluoride varied from those equivalent to therapeutic doses to toxic doses, and the duration of the treatment was from 15 days to 33 months. No significant modification in serum calcium, phosphorus, and alkaline phosphatase was reported. An increased serum osteocalcin level was noted in ewes. Evidence for hyperparathyroidism was found in some but not all animal models. Studies performed in the rat reported that fluoride had different effects on the periosteal and endosteal bone. An increase in the extent of eroded surfaces was observed in all experimental studies, except one in the mouse. Increases in osteoid parameters and in the number of osteoblasts were noted in mouse, cat, pig, and ewe. Only one study, carried out in dogs, mentioned a decrease in osteoid parameters. Most of the authors reported a mineralization defect due either to a modification in the composition of the bone matrix or to a low calcium intake. The formation period was augmented during fluoride treatment but, at a fluoride dose equivalent to therapeutic doses, this augmentation was mainly due to an increased active formation period. In contrast, at a fivefold greater dose, it was due to an increased inactive formation period. The augmentation of bone volume after fluoride treatment was attributed to an unbalanced coupling between resorption and formation in favor of formation. All these experimental studies support the conclusion that fluoride induces a stimulation of the birthrate of osteoblasts, but at high doses decreases their activity.

Urinary excretion of glycosaminoglycans, hydroxyproline and hydroxylysine in rabbits after excessive ingestion of fluoride

Urinary levels of glycosaminoglycans (GAG) and hydroxyproline from normal and fluoride treated rabbits were estimated. The hydroxylysine content of serum and urine of rabbits after excessive ingestion of fluoride was also investigated. There was a progressive decrease in GAG content, reduction in hydroxylysine, whereas the hydroxyproline content was increased after fluoride ingestion. Enhanced hydroxyproline in urinary excretion is due to collagen breakdown after fluoride ingestion. The reduction in hydroxylysine content is due to reduced collagen cross-link formation. The report suggests the possibility of using the urinary levels of GAG or hydroxyproline or hydroxylysine as an index of fluoride intoxication.

Cellular and histochemical characteristics of osteoid formed in experimental fluoride poisoning

The present study on the cellular and histochemical characteristics of osteoid formed in iliac crest bone during fluoride poisoning in rabbits was carried out as there is no information available to date either on its structural or biochemical characteristics. Osteoid formation in bone is prevalent both in fluorosis and in sodium fluoride therapy for osteoporosis. The report provides evidence which indicates that fluoride induces osteophytic activity leading to the formation of cartilagenous loci (fibrocartilage) in bone, the matrix of which is loaded with glycosaminoglycans (GAG) and proteoglycans. The occurrence of dermatan sulphate is demonstrated histochemically. Accumulation of dermatan sulphate in the cartilagenous matrix possibly prevents the normal process of mineralization.

Excessive ingestion of fluoride and the significance of sialic acid: glycosaminoglycans in the serum of rabbit and human subjects

The levels of sialic acid and glycosaminoglycans were explored in the sera of rabbit and human subjects who ingested fluoride and had clinical manifestation of fluorosis. Changes observed in the level of these chemical constituents in sera possibly reflect changes occurring in calcified and noncalcified tissues due to fluoride intoxication. The ratio of sialic acid content vs glycosaminoglycans revealed there was a 50% reduction in rabbit and human sera. The test is recommended for evaluating the prognosis of fluoride poisoning/fluorosis.