Effects of sulfonamide on the pituitary-thyroid gland. 2. Morphological changes of thyrotrophs in anterior pituitary gland.

Light and electron microscopic observations were made on the anterior pituitary gland of male Wistar rats treated with daily oral administrations of sulfonamide at a dose of 2 g/kg for 30 consecutive days. Several rats were treated with the same dose by the same route for 15 days and then put to the restoration experiment for the equal number of days. Histologically, increase and swelling of thyrotrophs, the cytoplasmic granules of which were stainable with PAS and AF, were found after the 7th or 10th day of treatment. On the 30th day, very large vacuoles were seen in the cytoplasm of these swollen thyrotrophs. On the ultrastructural observation of the cytoplasm of these cells, rough-surface endoplasmic reticulum were well developed with dilated cisternae which varied a great deal in size, and well-developed Golgi apparatus were seen. Many electron-dense round bodies were found in the variously dilated cisternae of rough-surface endoplasmic reticulum. These structures were recognized in some parts of the cisternae of rough-surface endoplasmic reticulum as early as on the 7th or 10th day of sulfonamide treatment. On the 30th day, there were autophagosomes and myelin figures in the cytoplasm of several swollen thyrotrophs. From these results, it is concluded that so-called "thyroidectomy cells" were found after the 5th or 7th day of the high-dose administration of sulfonamide and more and more increased in number with the repeat of administration. These changes tended to revert in the restoration period.