Effect of selenium supplementation on antioxidant indices and metabolism-related hormones in rats exposed to heat stress

High temperature causes oxidative stress in the body of animals. Selenium is a trace mineral that affects the health and performance of the body in stressful conditions. There are limited studies on the effects of different doses of selenium in long-term heat stress conditions on physiological parameters and health indicators. This study was conducted to determine the effects of different doses of selenium from selenium-methionine supplement on the antioxidant status (glutathione concentration, activity of superoxide dismutase and glutathione peroxidase), liver and kidney health index (the activity of transferase enzymes and creatinine concentration) and concentration of metabolism-related hormones (insulin, cortisol, triiodothyronine and tetra-iodothyronine). In a completely randomized design, 25 female rats were randomly divided into five groups and five replicates. Five rats were placed at standard temperature during the experiment period and the rest of the rats were placed under heat stress (38 ± 2 °C for 6 hours/day). Rats in the negative control group (without heat stress) and positive control (heat stress) were fed with standard pellets without additive and the other three groups were fed with standard pellets plus 0.15, 0.30 and 0.45 mg selenium/kg as a selenium-methionine supplement for 30 days. Rats receiving selenium had more hemoglobin and alanine transaminase enzyme activity (P=0.001) compared to the positive control group. Cortisol concentration in the positive control group was higher than the negative control group (P=0.001). Adding selenium to the diet of rats under heat stress decreased (P=0.001) the concentration of cortisol, and increased the concentration of insulin and triiodothyronine compared to the positive control group. The serum malondialdehyde of the positive control was higher than the negative control and other experimental groups (P=0.001). According to the results of this study, heat stress causes oxidative stress in the body and causes changes in the hormonal concentration and the activity of the body's enzymes. In overall, it can be concluded that higher selenium supplementation (0.45 mg/kg) is optimal for improving the liver and kidney indices, hormone concentration and antioxidant response in rats under heat stress conditions.