Animal models are widely used in biology and the findings of animal research are traditionally projected to humans. However, recent publications have raised concerns with regard to what extent animals and humans respond similar to physiological stimuli. Original data on direct in vivo comparison between animals and humans are scarce and no study has addressed this issue after exercise. We aimed to compare side by side in the same experimental setup rat and human responses to an acute exercise bout of matched intensity and duration. Rats and humans ran on a treadmill at 86% of maximal velocity until exhaustion. Pre and post exercise we measured 30 blood chemistry parameters, which evaluate iron status, lipid profile, glucose regulation, protein metabolism, liver, and renal function. ANOVA indicated that almost all biochemical parameters followed a similar alteration pattern post exercise in rats and humans. In fact, there were only 2/30 significant species × exercise interactions (in testosterone and globulins), indicating different responses to exercise between rats and humans. On the contrary, the main effect of exercise was significant in 15/30 parameters and marginally nonsignificant in other two parameters (copper, P = 0.060 and apolipoprotein B, P = 0.058). Our major finding is that the rat adequately mimics human responses to exercise in those basic blood biochemical parameters reported here. The physiological resemblance of rat and human blood responses after exercise to exhaustion on a treadmill indicates that the use of blood chemistry in rats for exercise physiology research is justified.
Recent studies have consistently supported the active role of blood in mediating biochemical and physiological tissue adaptations. However, no study has investigated the possible contribution of circulating factors in an exercise setting. The aim of the study was to investigate the role of circulating factors in exercise adaptations by chronically administering to sedentary animals blood plasma collected from acutely exercised animals. Phase 1: Blood plasma was collected from rats that swam to exhaustion and from sedentary rats. Phase 2: Other rats were divided into two groups (n = 20 per group): the first group involved rats that were injected intravenously with blood plasma originating from rats that previously swam to exhaustion, the second group consisted of rats that were injected intravenously with blood plasma originating from sedentary rats. Tail‐vein injections (2 mL/kg) were performed daily for 21 consecutive days. Inflammatory markers (C‐reactive protein, interleukins‐1α, 2, 6, 8, 10 and tumor necrosis factor‐a) were measured in blood plasma, muscle, and adipose tissue. Sedentary rats administered with plasma from exercised rats had significantly higher levels in all inflammatory markers measured in blood, skeletal muscle and adipose tissue, compared to the sedentary rats administered with resting plasma. Our data demonstrate that administration of “exercised” blood to sedentary rats induced inflammation in plasma, muscle and adipose tissue. Exercise adaptations are not solely due to intrinsic processes in muscle or adipose tissue. Blood factors also play a crucial role in mediating signals for tissue adaptations.
The rat adequately mimics human responses to exercise in basic blood redox/inflammatory profile, yet this is not the case after exercise combined with vitamin C administration.
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