The aim of the study was to evaluate the changes in selected metabolites of arachidonic acid under the conditions of endotoxin fever and pyrogenic tolerance in pigeons. On the first day of the study experimental birds (n = 18) were intravenously injected with Escherichia coli LPS at a dose of 10 µg/kg b.w. (endotoxin fever induction), whereas at the same time the controls with sterile physiological saline. On the second and the third days of the study, in the pigeons previously injected with LPS the state of pyrogenic tolerance was evoked. For this purpose, on the second day twelve birds from experimental group received E. coli LPS again (10 µg/kg b.w.). On the third day of the study six from twelve experimental birds were injected with a consecutive, final dose of endotoxin. Each four-and-a-half hours after consecutive LPS injections, blood samples were collected for laboratory examinations. Prostaglandin (PGE₂ and PGF₂α), leukotrien B4 (LTB₄) and tromboxan B2 (TXB₂) concentrations were investigated in the blood sera. In response to the single LPS injection a distinct stimulation of the PGE₂ and PGF₂α synthesis was observed, which probably shows a participation of these eicosanoids in the induction of fever in the pigeons. There was also observed an increase in the LTB₄ production, an important chemotactic factor for leukocytes and a decrease in the TXB₂ concentration, which may be associated with its participation in a disseminated intravascular coagulation (DIC) visibly enhanced during endotoxemia. However consecutive LPS injections caused a distinct suppression of PGE₂ and PGF2α synthesis, and an increase in the TXB₂ concentration, probably resulting from a lysis and then resorption of endovascular blood clots composed of thrombocytes. The LTB₄ concentration was still rising in the conditions of pyrogenic tolerance, possibly indicating a strong activation of phagocytic blood cells of which a direct consequence is usually an increased migration of these cells to places with inflammatory processes and an activation their killing ability.
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