Does Salivary Function Decrease in Proportion to Radioiodine Dose?

Objectives: This study was conducted to investigate the dose-response characteristics of radioiodine on salivary glands and to investigate the mechanism responsible for radioiodine-induced salivary glands toxicity. Methods: Twenty-four mice were divided into six groups: 0, 0.05, 0.10, 0.20, 0.40, and 0.80 mCi/20 g mouse, administered orally. Mortalities were noted 12 months after radioiodine administration. Body weights, gland weights, salivary lag times, flow rates, and changes in ^99mTc pertechnetate were recorded. Histopathological changes and mRNA expressions were also evaluated, and immunohistochemical analysis and apoptotic assays were performed. Results: Survival rates, body weights, gland weights, and flow rates decreased, and lag times increased on increasing radioiodine dose. Animals administered radioiodine showed acinar atrophy, striated duct dilations, and lymphocytic infiltration in glands and irregular destruction of epithelial surfaces of tongue. The uptake and excretion of ^99mTc pertechnetate were impaired by radioiodine. Immunohistochemical analysis showed that numbers of salivary epithelial, myoepithelial, and endothelial cells decreased and that numbers of ductal cells increased with radioiodine dose. Oxidative stress biomarker levels increased; reactive oxygen species scavenger levels decreased; and numbers of apoptotic cells increased in animals exposed to higher radioiodine doses. Conclusion: These dose-related, long-term effects on salivary gland should be taken into account when determining radioiodine doses. Level of Evidence: NA Laryngoscope, 130:2173–2178, 2020.