Exercise and stress protein in blood 1 Elevation of body temperature is essential factor for exercise - increased extracellular 1 heat shock protein 72 level in rat plasma 2 3

1 This study examined whether the exercise-increased extracellular heat shock protein 72 2 (eHsp72) level in rat was associated with body temperature elevation during exercise. In all, 3 26 female Sprague-Dawley rats (3 months old) were assigned randomly to control (CON, n = 4 8), exercise under warm temperature (WEx, n = 9), or exercise under cold temperature (CEx, 5 n = 9). The WEx and CEx were trained respectively at 25oC or 4oC for nine days using a 6 treadmill. Before and immediately after the final exercise bout, the colonic temperatures 7 were measured as an index of body temperature. The animals were subsequently anesthetized 8 and blood samples were collected and centrifuged. Plasma samples were obtained to assess 9 their eHsp72 levels. Only the colonic temperature in WEx was increased significantly (P < 10 0.05) by exercise. The eHsp72 level in WEx was significantly higher (P < 0.05) than that of 11 either the CON or CEx. However, no significant difference was found between CON and 12 CEx. Regression analyses revealed that the eHsp72 level increased as a function of the body 13 temperature. In another experiment, the eHsp72 level of animals with body temperature that 14 was passively elevated through similar kinetics to those of the exercise was studied. Results 15 of this experiment showed that mere body temperature elevation was insufficient to induce 16 eHsp72 responses. Collectively, our results suggest that body temperature elevation during 17 exercise is important for induction of exercise-increased eHsp72. In addition, the possible 18 role of body temperature elevation is displayed when the exercise stressor is combined with 19 it. 20 21