The authors were investigating the histochemical and electron microscopic characteristics of thyreocytes in pinealectomized rats treated with melatonin, prior to irradiation. They observed that the animals that did not receive melatonin show a higher degree of the destruction appearing at the level of all ultrastructural organelles and a very low expression of the DNA and RNA histochemical reaction. These results suggest the role of melatonin in the determination of the thyreocyte behaviour under given irradiation conditions.

The authors investigated histological characteristics of the thyroid gland in irradiated rats under the conditions of anepiphysia. Pseudo-epiphysectomized rats and epiphysectomized rats were irradiated in toto with a single dose of 8 Gy gamma irradiation. The animals were decapitated on the 121st day of the postoperative period, in other words, on the 6th day following irradiation. The animals with an intact epiphysis showed significant changes in the histological structure of the thyroid, but they were of a considerably lesser intensity when compared to the changes observed in epiphysectomized rats. On the basis of the differences observed in behavioural characteristics as well as the degree of mortality, we propose that pineal gland absence has determined the behaviour of the glandular parenchyma, as well as of the whole organism in the given conditions.