Differences in Exercise Capacity and Physiological Responses in Wistar Rats among Breeders

In animal experiments aimed at extrapolation to humans, it is essential to ensure the reproducibility of experiments and universality between animals and humans. However, among animals with the same generic name but from different breeders, which is to say different stocks, even resting physiological conditions, such as genetics, do not coincide, and, therefore, exercise capacity and physiological responses may also vary. To address this issue, we examined the differences in exercise capacity and exercise-induced metabolic and endocrine responses among stocks of Wistar rats using an established treadmill running model for rodents, which mimics physiological responses in humans. Wistar rats from four breeders were acclimated to treadmill running and then had a catheter inserted into their external jugular veins. Subsequently, the rats were subjected to an incremental treadmill running test (IRT). We found that there were significant differences in the exercise capacity among Wistar rats from different breeders. Additionally, the dynamics of blood lactate, glucose, and adrenocorticotropic hormone levels during the IRT were found to vary among the Wistar rats from different breeders; only one stock showed human-type exercise-induced physiological responses. These results indicate that Wistar rats could have different capacities for and physiological responses to the same exercise depending on their stocks. Thus, the selection of the stock of experimental animals may affect the validity of the results when verifying exercise effects.