Effects of physical training on febrile and acute‐phase responses induced in rats by bacterial endotoxin or interleukin‐1.

1. We investigated the effect of physical training on febrile and acute‐phase responses induced in rats by intravenous (I.V.) injection of bacterial endotoxin or human recombinant interleukin‐1 beta (IL‐1). Physical training was performed by swimming for 1 h per day, 5 days a week. After four weeks of training, animals were used in the experiments. 2. The I.V. injection of endotoxin produced a febrile response in the trained group but not in the control group. However, there were no statistically significant differences between febrile responses induced by the I.V. injection of IL‐1 in the control and trained groups. 3. The I.V. injection of endotoxin significantly decreased the plasma concentration of iron and zinc and increased the plasma fibrinogen concentration in both the control and the trained groups. However, the decreases in the plasma iron and zinc concentrations in the trained group were significantly greater than those in the control group. The I.V. injection of endotoxin increased the circulating leucocyte count in the only trained group. 4. The I.V. injection of IL‐1 significantly decreased the plasma concentration of iron and zinc and increased the plasma fibrinogen concentration and the circulating leucocyte count in both the control and the trained groups. However, between the two groups, no significant differences in the values of acute‐phase reactants were observed. 5. The present results suggest that the ability to produce cytokine(s) to induce febrile and acute‐phase responses is enhanced by physical training. However, physical training has no effect on the febrile and acute‐phase responses induced by IL‐1.