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Increased exposure to fluorine-containing compounds leads to accumulation of fluorides in hard tissues of bones and teeth, which may result in numerous skeletal and dental disorders. This study evaluates the influence of methionine and vitamin E on fluoride concentration in bones and teeth of rats subjected to long-term exposure to sodium fluoride in drinking water. The study was conducted in 30 3-month-old female Wistar FL rats. The animals were divided into five groups, six rats per group. The control group consisted of rats receiving only distilled water as drinking water. All other groups received NaF in the amount of 10 mg/kg of body mass/day in their drinking water. In addition, respective animal groups received: NaF + Met group--10 mg of methionine/kg of body mass/day, NaF + Met + E group--10 mg of methionine/kg of body mass/day and 3 mg of vitamin E (tocopheroli acetas)/rat/day and NaF + E group--3 mg of vitamin E/rat/day. Femoral bones and incisor teeth were collected for the study, and the fluoride concentration was determined using a fluoride ion-selective electrode. Fluoride concentration in both bones and teeth was found to be higher in the NaF and NaF + Met groups compared to the control group. In groups NaF + Met + E and NaF + E, the study material contained much lower fluoride concentration compared to the NaF group, while the effect was more prominent in the NaF + E group. The results of the studies indicate that methionine and vitamin E have opposite effects on accumulation of fluorides in hard tissue in rats. By stimulating fluoride accumulation, methionine reduces the adverse effect of fluorides on soft tissue, while vitamin E, which prevents excessive accumulation of fluorides in bones and teeth, protects these tissues from fluorosis. Therefore, it seems that combined application of both compounds would be optimal for the prevention of the adverse effects of chronic fluoride intoxication.

We studied chronic fluoride intoxication in 10 villages of Udaipur receiving F emissions from phosphate fertilizer factories. Although fluoride remained below permissible limit in most of the drinking water samples, the incidence of fluorosis in adults as well as in children was surprisingly high. Khemli appeared to be the most affected village (with48% cases) where, about 93% of 2 h air samples contained fluoride above 2.0 μg m(-3) and crops and vegetable F ranged from 27.5 to 143.4 μg g(-1). Concentrations of fluoride and inorganic P in urine showed asynchrony and were well linked with prevalence of fluorosis. The study indicated that air-borne fluoride was the major factor for higher prevalence of fluorosis in these rural areas.

We examined the effects of fluoride intoxication on certain blood plasma biochemical indices in rats. Fortyeight adult female Wistar rats weighing 123-142 g were divided into eight groups: two control groups (0 and 28 days) and six experimental groups, namely sham-injected animals (vehicle), injected with pineal proteins (PP) and melatonin (Mel), intoxicated with fluoride (F), and also F+PP and F+Mel groups. Fluoride (150 ppm, per os administration with drinking water), melatonin (10 mg/kg, i.p.), and PP (100 μg/kg, i.p.) were administered daily for 28 days. Blood samples were collected at the end of experiments to estimate plasma [Na+] and [K+], alkaline phosphatase (ALP) activity, and levels of glucose and proteins in different animal groups. The plasma [K+] and [Na+], and ALP activity were significantly (P < 0.05) elevated in F-treated animals, as compared with others. Administration of PP and Mel in F-treated rats caused significant (P < < 0.05) reduction of [Na+], [K+], and ALP levels. Interestingly, PP and Mel administrations resulted in noticeable (P < 0.05) increases in the plasma glucose level in F-intoxicated animals, as compared to other groups. These findings convincingly indicate that PP and Mel exert ameliorative effects on fluoride-induced adverse changes in certain biochemical parameters in rats.

High-resolution solid-state 19F NMR method has been used to examine the chemical structural forms of fluorine introduced into the bone tissue of experimental animals (Vistar rats) exposed to 30 day fluoride inhalation. It is shown that in the bone tissue three structural forms of fluorides are deposited: a solid phase of F-apatite and mobile nanoparticles of CaF2 and MgF2 (or KMgF3) with the ratio of fluorine concentration in these three forms ∼2:2:1. During the following 30 day rehabilitation this ratio remains constant, the total fluorine content in the bone tissue decreases ∼3 times and the F-apatite phase transforms into disordered (F, OH)-apatite. A protective effect of the zeolitic enterosorbent (klinoptilolite) on fluorine binding in the intoxication process was found, as well as the promotional effect of this enterosorbent on fluorine excretion during the postfluoride rehabilitation.