Parathyroid glands, calcium, and vitamin D in experimental fluorosis in pigs

Abstract

The purpose of this study was to determine whether total serum calcium, parathyroid gland structure, and/or levels of parathyroid hormone, 1,25 and 24,25 DHCC, are altered in pigs with dental and skeletal fluorosis. Eight experimental animals receiving 2 mg F-/kg b.w. per day from age 8-14 months were compared with eight controls. Concentrations of plasma fluoride and total plasma calcium were assessed at intervals throughout the experiment and during a 48 hour period at day 110-111 of the experiment. At the same time, concentrations of immunoreactive parathyroid hormone were measured using a homologous labeled antibody for porcine hormone, and a radioimmunoassay was used to assess concentrations of 1,25 DHCC and 24,25 DHCC. Parathyroid tissue volumes were assessed at the end of the experiment by quantitative histology using volumetry and point counting. Plasma fluoride increased from 0.0007 +/- 0.0001 mmol/liter to 0.0127 +/- 0.002 mmol/liter in pigs receiving fluoride. In spite of this increase, total plasma calcium remained the same throughout the experiment. Volumes of parathyroid tissue, and levels of circulating parathyroid hormone 1,25 DHCC and 24,25 DHCC, were not significantly changed. It was therefore concluded that disturbance of calcium homeostasis is not an obligatory finding in dental and skeletal fluorosis and consequently does not play an essential role in the pathogenesis of these hard tissue lesions.

The levels of trace elements and selected vitamins in goats with chronic fluorosis

“…Serum vitamin D levels in ruminants with fluorosis were measured for the first time in this study according to our knowledge of the literature, and they were not changed significantly according to our findings. These findings are consistent with the findings of an experimental study in pigs (15). In the present study, adequate levels of vitamin D were determined, which facilitates absorption of Ca from the gastrointestinal tract.…”

“…In the present study, adequate levels of vitamin D were determined, which facilitates absorption of Ca from the gastrointestinal tract. Similar findings were reported in experimental studies by other researchers (14,15). However, the same researchers reported that disturbance of Ca homeostasis is not a necessary finding in dental and skeletal fluorosis and consequently vitamin D does not prevent the deleterious effects of F on motor coordination and teeth.…”

“…In addition, vitamin D plays a role in the amelioration of fluoride-induced toxicity (14). Various researchers have also reported a relationship between F and vitamins (9,(15)(16)(17) and between vitamins and the treatment of fluorosis (9)(10)(11). However, studies in this respect in ruminants are very limited (8).…”

The Impact of Fluoride on Ameloblasts and the Mechanisms of Enamel Fluorosis

“…A level of 175 ppm F in drinking water is lethal for about one-third of the rats within 10 days when started at weaning; the remaining rats have stunted growth (Mullenix et al, 1995). No changes in plasma calcium were found in adult rats fed food pellets containing 450 mg F/kg for 8 wks (Appleton, 1994) or pigs receiving a daily oral dose of 2 mg F/kg body weight for 6 mos (Andersen et al, 1986). In the pigs, no changes in immunoreactive PTH and 1,25 vitamin D or 24,25 vitamin D metabolites could be found (Andersen et al, 1986).…”

“…No changes in plasma calcium were found in adult rats fed food pellets containing 450 mg F/kg for 8 wks (Appleton, 1994) or pigs receiving a daily oral dose of 2 mg F/kg body weight for 6 mos (Andersen et al, 1986). In the pigs, no changes in immunoreactive PTH and 1,25 vitamin D or 24,25 vitamin D metabolites could be found (Andersen et al, 1986). This indicates that, at those doses, fluoride does not interfere with calcium homeostasis.…”