Effect of moderate or high intensity exercise on hypothyroid rats exposed to acute stress.

Abstract

There are contradictory results about stress response in hypothyroidism and in exercising with variant intensities. We aimed to investigate the potential anxiolytic and protective effects of different intensities of exercise on acute psychological stress in hypothyroidism. Rats (N.=48) were divided as sedentary, moderate intensity (MIE) and high intensity exercise (HIE) groups. Rats were administered intraperitoneally with 6-n-propyl-2-thiouracil (PTU, 10 mg/kg) for 15 days to induce hypothyroidism. Starting by the 3rd week, treadmill exercise was performed moderately (30 min/day) or at high intensity (60 min/day) for 6 weeks, 5 days/week. At the end of the 8th week, exposure to water avoidance stress was used for induction of acute stress. Anxiety-like behavior was determined by holeboard test before and after stress inductions. Serum IL-1β and IL-6 assays, and myeloperoxidase activity (MPO), malondialdehyde (MDA), and glutathione (GSH) measurements, and histological analysis of heart, liver, stomach and small intestine were made. All groups showed increased anxiety-like behavior following acute stress induction. After acute stress induction, increased MPO and MDA levels in heart and elevated MPO activity in liver were inhibited in PTU-treated HIE group. In MIE rats, increased MPO and declined GSH levels of the gastric tissue and small intestine, and elevated MDA levels of gastric tissue were reversed in PTU-treated MIE group. Major histological changes that occurred by both intensities of exercise under stress condition were improved by PTU. Our results indicate that hypothyroid state may be protective against stress- and exhaustive exercise-induced oxidative damage.