Histological and histochemical appearance of livers and kidneys of rats after long-term treatment with different concentrations of sodium fluoride in drinking water.

After a review of the controversies in the literature, a histologic and histochemical study of the livers and kidneys of 48 albino rats was performed. The animals were placed on a diet containing 1 ppm NaF in demineralized drinking water, or 1, 10 or 100 ppm NaF in tap water during 90 or 180 days. The rats treated with fluoride did not present any abnormalities with respect to weight gain, morphology, behavior, and macroscopic appearance of the livers and kidneys compared to the control animals. Microscopic examination failed to reveal any morphologic alterations in either the cells or the mitochondria of the livers and kidneys. Histochemically, the polysaccharides, the protein reactive groups and the acid and alkaline phosphatases also failed to present any visible alterations. With respect to the lipids, the kidneys and livers of the rats treated for 90 days did not show any fat deposition, whereas those treated for 180 days showed zones of deposition of lipids in the livers and kidneys with different frequencies when compared with the control animals. The association between lipid infiltration and the presence of fluoride in the drinking water, however, was statistically significant only in the livers, hence, the hypothesis that fluorinated water accelerated this process in the treated animals cannot be excluded.