[Radioiodine administration for the production of an athyreotic animal model].

The resection of thyroid gland with radioiodine is a painless method to eliminate the Gl. thyroidea. By the present investigation it could be demonstrated that the thyroid gland of Wistar rats with a body mass between 100 and 500 g can be safely eliminated by administering them 2 doses of 18.5 MBq (0.5 mCi) 131I with a waiting period of 7 d in between. Application of 37.0 MBq (1.0 mCi) 131I once is, with regard to the radio-hygiene, to prefer, since the rats were contaminated on the surface when administering them iodine for the second time. The success of the experiment has been controlled in vitro and in vivo. Measuring the extirpated larynx region in the borehole of a gamma counter after a diagnostic labelling has been found to be an useful control method in vitro. Histological investigation of the larynx is extremely time-consuming. Besides it was not always possible to distinguish the single radio-iodine treated groups with this method. Since there were some animals showing residual thyroid tissue, the control by means of the development of the body masses cannot be recommended. Apart from this the development of the body masses depended very much on the surrounding temperature in which the animals were kept. The rectal temperature of the rats also depended on various external disturbances, so that this parameter failed to control the function of the thyroid gland.