Histological and Immunohistochemical Evaluation of Kidney Tissues of Rats Exposed to Different Chronic Fluoride Doses Pre- and Postnatally

Objectives: The aim of this study was to evaluate toxic effects and the histopathological changes of high doses of fluoridated water on kidney tissues of rats, that received chronic fluoride (F) doses pre and postnatally.
Methods: Female rats received 0, 30 and 100 ppm F ad libitum in drinking water, throughout the gestation and nursing periods. After the pups were born, and continued to administer fluoridated water ad libitum as three groups (control, 30 ppm F and 100 ppm F) and followed up for 1, 3 and 5 months, they were sacrified for determining their kidneys pathology. Rat kidney tissues were removed, sectionned and stained with hematoxylin and eosin (H&E) for the histological observation and stained with the terminal deoxyribonucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end labeling (TUNEL) assay (Roche, Mannheim, Germany) to detect any immunohistochemical changes and/or apoptosis in glomerular and tubular sections.
Results: F toxicity of the rats has detected in incisors as dental fluorosis. Histopathologic analyses of kidney tissues showed that severe cellular apoptosis increased due to fluorosis and the severity was dependent to F dosage. In 100 ppm F groups, the number of glomerular and tubular apoptotic cells were higher than control and 30 ppm F groups and statistically significant (p< 0.0001). In all groups, higher apoptosis values were detected in 5th month rats than 1st and 3rd month ones in glomerular and tubular sections (p< 0.05). Under this experimental condition, the transverse section of kidney of 5 month F exposed rats have shown tubular dilatations, glomerular atrophies and necrosis areas, vascular congesions and hemorrhagic regions.
Conclusions: In conclusion, at the high doses administered and prolonged exposure to F in drinking water, kidney tissues were affected adversely and F caused severe apoptosis in tubular and glomerular sections of rat kidney tissues.