EN
It is assumed that rT3 (3,3’,5’-triiodothyronine) antagonized the effect of 3.3’,5-triiodothyronine (T₃) and thyroxine (T₄). Non-thyroidal illnesses are associated with „low T₃ syndrome” and higher гТ₃ plasma levels. The aim of this preliminary investigation was to discover if rТ₃, which acts hypometabolically may have an attenuating effect on mice infected with Pasteurella multocida (P.M.). A dose of about 20 thousand of P. multocida bacteria per animal i.p. at a volume of 0.1 ml was applied. Reverse T₃ or T₄ were applied s.c. at a dose of 10 or 2 µg/animal, respectively, at 12 h after bacteria infection, and at 12 h intervals for 3 consecutive days. The survival time was measured 10 days after infection of P. multocida. The mean survival time was 75.6 ± 5.9, 92.4 ± 11.6 and 117.6 ± 16.2 h for animals receiving T₄ + P.m. (n=10), 0.9% NaCl + P.m. (n=10) or rT₃ + P.m. (n=15), respectively. Two mice treated with rT₃ survived. A significant differences (P≤0.05) was obtained only in groups treated with T₄ and rT₃. The results have shown that in comparison with T₄, rT₃ prolonged the survival time of mice infected with P. multocida. These results also confirm a different action of rT₃ and T₄.