Fig. 2. Time course of changes in manganese superoxide dismutase (MnSOD) activity in skeletal muscle of untreated, L-arginine-treated and L-NAME-treated rats during early and late acclimation 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<0.001 compared with the untreated group at the same time of cold acclimation.