Fig. 4. Time course of changes in glutathione peroxidase (GSH-Px) activity in the skeletal muscle of untreated, L-arginine-treated and L-NAME-treated animals during exposure to cold (4±1°C). ^*P<0.05, ^**P<0.01, ^***P<0.001 compared with the control maintained at room temperature (22±1°C). ^#P<0.05, ^##P<0.01, ^###P<0.001 compared with the untreated group at the same time of cold acclimation.