Enhanced chemotaxis of macrophages by strenuous exercise in trained mice: Thyroid hormones as possible mediators

Abstract

Exercise modulates the macrophage activity via ‘stress hormones’. Three experiments were performed. (1) The effect of strenuous exercise performed by trained mice on macrophage chemotactic capacity was evaluated; (2) peritoneal macrophages from control mice were incubated with plasma from exercised mice or control mice and the differences in chemotaxis were measured; (3) changes in plasma T₃ and T₄ levels after exercise were measured, and the effect of incubation with the post-exercise levels of plasma T₃ and T₄ on chemotaxis was then studied in vitro. A 10⁴-fold higher concentration of each hormone was also evaluated. Exercise provoked an increase in chemotaxis (104 ± 35 vs. 47 ± 11 in controls). Incubation with plasma from exercised mice led to an increased level of chemotaxis. Incubation with concentrations of T₃ and T₄ similar to those observed in post-exercise plasma (T₃, 2.3 nmol l^-1; T₄, 84 nmol l^-1) enhanced chemotaxis with respect to incubation with the basal concentrations of the hormones in control animals. A 10M⁴-fold concentration of T₄ reversed this effect. It is concluded that thyroid hormones stimulate macrophage chemotaxis. Also, these data support the hypotheseis that thyroid hormones may be involved in exercise-induced stimulation of chemotaxis.