Objective: 

The responses to stress show discrepancy in hypothyroidism. The aim was to study the impact of regular exercise on the peripheral tissues of hypothyroid rats exposed to acute stress.

Methods: 

Male Sprague Dawley rats were administered intraperitoneally with 6-n-propyl-2-tiouracil (PTU, 10 mg/kg) for 15 days to induce hypothyroidism. Exercise was performed on a treadmill for 6 weeks at a moderate intensity (MIE; 30min/5days/week) or high intensity (HIE; 60min/5days/week), but the control group did not exercise. Six weeks later, rats were exposed to a 30-min water avoidance stress and then the rats were decapitated to obtain samples of heart, stomach, liver and small intestine for the measurement of lipid peroxidation (LP), gluthatione (GSH) levels, myeloperoxidase (MPO) activity and for histological analysis. Data were analyzed by Student's t test or ANOVA.

Results: 

MPO activities, LP and GSH levels in the tissues of control rats and stressed rats with hypothyroidism were not different. In hypothyroid rats with MIE, MPO levels were increased in the stomach and small intestine as compared to control group (p<0.05), while in HIE rats with hypothyroidism cardiac and hepatic MPO activities and LP levels were decreased (p<0.01-0.001). IL-1alpha and IL-6 levels were decreased in exercised rats with hypothyroidism. The histological results were parallel to the biochemical data.

Conclusions: 

Results revealed that stress did not further increase oxidant damage in tissues affected by hypothyroidism. Moderate exercise enhanced oxidant damage parameters in the gastrointestinal tissues, while high intensity exercise in hypothyroidism depressed oxidant damage in the cardiac and hepatic tissues.