Internalization and heterochromatic localization of 3H-di-iodothyrosine (T2) in the unicellular organism Tetrahymena and rat thymocytes.

Diiodotyrosine (T2) binds in Tetrahymena to ciliary membranes and enters the cell by endocytosis and also by other means (diffusion?). It can be found in the nucleus within, always in heterochromatic localization. The mitochondrial localization is also characteristic. In rat lymphocytes T2 is present in the cytoplasm independently from vesicles and it appears in the nucleus later than in Tetrahymena but invariably in heterochromatic localization. It can also be seen in the chromosomes of mitotic cells.