Ultra Structural Changes in Rat Thyroid Gland Exposed to Fluoride

Abstract

The present study elucidate ultrastructural effect of fluoride on the thyroid follicular cells. Wistar albino rats were treated with sodium fluoride in doses of 300 and 600 mg/kg bodyweight/day by oral gavage for 40 days. The controls were given 1ml double distilled water/kg body weight /day for the same period. The animals were anaesthetized and thyroid glands were excised and processed for transmission electron microscopic examination. The thyroid gland of control rat showed flat follicular cells along with interfollicular connective tissue on the basal membrane. The nuclei appeared euchromatic with regular and well-formed nuclear membrane. The cytoplasm contained rough endoplasmic reticulum, mitochondria and mast cell with many small dense granules. In the fluoride treated animals, thyroid follicular epithelium had reduced cell height and low colloid content. The basal membrane was ill defined. The nuclei were irregular, heterochromatic with deformed nuclear membrane. The cytoplasmic disorganization was observed with scattered stacks of rough endoplasmic reticulum and loss of mitochondria. The polymorphic dense lysosomal granules and vacuoles were visible. The parafollicular cells with multiple rounded euchromatic nuclei were present. In the higher dose group, thyroid gland showed increasing interfollicular spaces and fusion of follicles.