The magnitude of physical exercise-induced hyperthermia is associated with changes in the intestinal permeability and expression of tight junction genes in rats

Abstract We investigated whether the magnitude of exercise-induced hyperthermia influences intestinal permeability and tight junction gene expression. Twenty-nine male Wistar rats were divided into four groups: rest at 24 °C and exercise at 13 °C, 24 °C or 31 °C. The exercise consisted of a 90-min treadmill run at 15 m/min, and different ambient temperatures were used to produce distinct levels of exercise-induced hyperthermia. Before the experimental trials, the rats were treated by gavage with diethylenetriaminepentaacetic acid labeled with technetium-99 metastable as a radioactive probe. The rats' core body temperature (TCORE) was measured by telemetry. Immediately after the trials, the rats were euthanized, and the intestinal permeability was assessed by measuring the radioactivity of blood samples. The mRNA levels of occludin and zonula occludens-1 (ZO-1) genes were determined in duodenum samples. Exercise at 24 °C increased TCORE to values close to 39 °C, without changing permeability compared with the resting trial at the same environment. Meanwhile, rats’ TCORE exceeded 40 °C during exercise at 31 °C, leading to greater permeability relative to those observed after exercise in the other ambient temperatures (e.g., 0.0037%/g at 31 °C vs. 0.0005%/g at 13 °C; data expressed as medians; p