Abstract

In rats which received drinking water containing 0, 3, 6, 12, 25 ppm NaF (F-) for 20 months, hyperplastic nodules, consisting of thyroid parafollicular cells (C cells) appeared in all F- groups, particularly in those which received 12 and 25 ppm. By immuno-histochemistry and electron microscopy, both calcitonin and characteristic secretary granules were detected in the cytoplasm of these hyperplastic cells. This morphological result was substantiated by the striking increase in the serum value of calcitonin, seen simulataneously in rats with hyperplasia of parafollicular cells. Furthermore, whereas the thyroid follicles were larger in size in the F-groups than in controls, the differences were not markedly significant.

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