Both selenium, as an effector and regulator of antioxidative enzymes activity, and thyroid hormones are potent immunomodulators. Besides, selenium incorporated into iodothyronine deiodinases is involved in the thyroid function and thus indirectly regulates the immune response. Studies of the mutual infl uence of selenium and thyroid hormones on the immune response are scarce, hence we analyzed the effects of an iodothyronine deiodinases blocker, propylthiouracil (PTU), and selenium defi ciency on the function of peritoneal macrophages, and titer of naturally occurring anti-sheep red blood cells (SRBC) IgM antibodies in juvenile rats.The experiment was carried out on 64 Wistar male rats allotted to 4 groups: controlselenium adequate PTU-group; selenium adequate, PTU+ group; selenium defi cient, PTU-group; and selenium defi cient, PTU+. The selenium adequate and selenium defi cient groups were fed a diet containing 0.334 and 0.031 mg Se/kg, respectively. PTU+ groups received PTU (150 mg/L) in drinking water. After 3 weeks, thyroxine (T 4 ), triiodothyronine (T 3 ), and thyroid stimulating hormone (TSH) were determined. The animals having "intermediate" concentrations of T 3 (1.56-1.69 nmol/L) and T 4 (41-50 nmol/L) were excluded from further analysis. Thus, PTU+ groups included hypothyroid animals (T 3 ≤1.55 nmol/L; T 4 ≤40 nmol/L), while PTU-groups included euthyroid rats (T 3 ≥1.70 nmol/L; T 4 ≥50 nmol/L). Both groups of selenium defi cient rats had, when compared to the control group, a signifi cantly lower activity of glutathione peroxidase GPx1 and GPx3. Neither selenium defi ciency nor PTU infl uenced the adherence of peritoneal macrophages. Selenium defi ciency signifi cantly decreased the peroxide synthesis in macrophages and signifi cantly increased the titer of anti-SRBC IgM. Hypotyroidism alone or in combination with selenium defi ciency had no infl uence on these parameters.

In this work there was investigated the influence of selenium and deodinases blockers on juvenile rats body weight during three months. The experiment was carried out on 64 rats divided into eight groups with eight individual animals per group. Following groups were formed: 1. Se+PTU-IA- (control group), 2. Se+PTU+IA+, 3. Se+PTU+IA-, 4. Se+PTU- IA+, 5. Se-PTU-IA-, 6. Se-PTU+IA+, 7. Se-PTU+IA- and 8. Se-PTU-IA+. The groups labeled (Se+) were selenium adequate and they were fed with food that contained 0.334 mg Se/kg. The groups labeled (Se-) were selenium deficient and obtained food with 0.031 mg Se/kg. As deiodinases blockers there were used propylthiouracil (PTU+) in a dose of 150 mg/L of drinking water and iopanoic acid (IA+) in a dose of 6 mg/100 g TM intraperitoneally. Body weight of experimental rats was measured every seven days. After three weeks of treatment there were taken blood samples of animals from all experimental groups and following parameters were determined: selenium concentration in blood, thyroxine (T4), triiodothyronine (T3) and thyroidstimulating hormone (TSH) in blood plasma. Analysis of the samples showed that the animals from the groups treated with PTU had lower body weight in regard to the control group, as well as lower concentration of T3 and T4 in plasma. Selenium deficient rats had lower average body weight compared to the selenium adequate ones after three weeks, but there were no differences in thyroid hormones concentration. The lowest average body weight was noticed in selenium deficient rats groups treated with PTU. [Projekat Ministartsva nauke Republike Srbije, br. TR31050 i br. TR31003]