Comparative results of thyroid cryoablation in SHR and vistar rats

Introduction. Today, cryosurgery is considered as a promising minimally invasive approach to the treatment of benign nodules of thyroid gland. Blood circulation in the tissue can affect the effectiveness of cryoablation preventing decline of the temperature. This is true for the thyroid gland, which belongs to organs with a high blood circulation rate. The SHR rat can be used for modeling the processes of thyroid cryoablation in people with essential hypertension, which makes it possible to obtain calculated data on reaching the target freezing temperature in patients with arterial hypertension. Aim of the study – make a comparative assessment of histological characteristics of thyroid gland tissue in hypertensive SHR rats and normotensive Wistar rats after cryoablation. Materials and methods. In the experiments, SHR and Wistar rats weighing 250–280 g were used. Cryodestruction of the thyroid gland was carried out in intact animals and rats, which were administrated with a 0.1 % solution of propylthiouracil to induce diffuse thyroid hyperplasia. The operation was performed under general anesthesia. Cryotherapy was carried out for 40 s once on the left lobe of the thyroid gland using a copper cryoprobe, which was cooled to the temperature of liquid nitrogen. On day 21, the animals were taken out of the experiment; the thyroid gland were taken and used for histological studies. Results. It was found that at the site of cryotherapy in gland samples of animals of both lines on day 21, a cone-shaped zone of fibrosis was formed, in which the parenchyma of the gland was replaced by connective tissue with pronounced vascularization and insignificant lymphocytic-histiocytic infiltration. The mean area of fibrosis did not differ significantly between the groups of intact SHR and Wistar rats. After cryoablation of glands with administration of propylthiouracil, a decrease in the area of fibrotic changes was observed: in Wistar rats – by 2 times, in SHR rats – by 3–4 times. Conclusions. Parameters of blood circulation in arterial hypertension did not significantly affect the result of thyroid gland cryoablation in rats. However, after induction of tissue hyperplasia with propylthiouracil, an increase in gland resistance to cryodestruction is observed, which should be taken into account when choosing a cryotherapy regimen.