sodium-perchlorate and Hyperplasia

Both perchlorate and arsenate are environmental contaminants. Perchlorate is a definitive thyroid disruptor, and arsenic may disrupt thyroid homeostasis via multiple pathways. To evaluate the effects of sodium perchlorate and sodium arsenate on thyroid function and possible interactions between them, zebrafish (Danio rerio) were exposed to sodium perchlorate (10 and 100 mg/L), sodium arsenate (1 and 10 mg/L), and the mixture sodium perchlorate + sodium arsenate (10 + 1 and 100 + 10 mg/ L) for up to 90 days. At day 10, 30, 60, and 90, fish were sampled and analyzed forthyroid histopathological end points including follicular cell height, follicle size, colloid size, colloid depletion, hyperplasia, and angiogenesis. Effects on epithelial cell height (hypertrophy) were seen as early as 10 days after exposure. Perchlorate induced changes in all parameters staring at 30 days of exposure. Prolonged perchlorate exposure induced angiogenesis, a relatively new marker of thyroid disruption. Sodium arsenate was less effective than sodium perchlorate in causing thyroid histopathologies, but transient responses were seen for hypertrophy, hyperplasia, and colloid depletion (% colloid). This is the first report of arsenate-induced effects on thyroid histopathology. However, because statistically significant effects were not consistently seen in all end points, evidence for arsenate as a thyroid disruptor remains equivocal. In general, the sensitivity of the following histopathological indicators for indicating thyroid perturbations is, in descending order: follicular cell height > percent of colloid area/follicle area > colloid area/follicular cell height > hyperplasia > angiogenesis > colloid area >follicle area = fish growth.

Topics: Angiogenesis Inducing Agents; Animals; Arsenates; Endocrine Disruptors; Environmental Exposure; Epithelial Cells; Hyperplasia; Lethal Dose 50; Perchlorates; Sodium Compounds; Thyroid Function Tests; Thyroid Gland; Time Factors; Water Pollutants, Chemical; Zebrafish

In a 46-week-experiment on 72 female mice the influence of peroral 1.2% sodium perchlorate application, total ionizing irradiation with 8 Gy on 5 consecutive days and their interaction on the pituitary-thyroid axis was studied by histological and stereological methods. It was observed that perchlorate alone caused long-term and strong hypothyroidism with hypertrophic and hyperplastic thyroid epithelial cells as well as pituitary thyrotropic cells. When only irradiation was used, no uniform changes in the structure and function of these cells could be detected. The interaction of perchlorate and irradiation showed similar effects as thyrostatics alone, with some exceptions; paradoxically, minor hyperplasia of thyrotropic as well as of parafollicular cells was observed. A high percentage of the follicular cell carcinoma was found after perchlorate application and after its combination with irradiation. No medullary carcinoma was found.

Topics: Animals; Epithelial Cells; Epithelium; Female; Gamma Rays; Hyperplasia; Hypertrophy; Mice; Mice, Inbred BALB C; Perchlorates; Pituitary Gland; Pituitary Gland, Anterior; Reference Values; Sodium Compounds; Thyroid Gland