Comparative Study of Urinary Catecholamine Metabolites by Chronic Cold Exposure and Exercise Training

Abstract

The present study was conducted to examine the sympathetic nervous activities, urinary catecholamine metabolitites, induced by running exercise in exercise-trained rats and chronic cold exposure in cold acclimated rats. The rats were randomly divided into the warm acclimated (WA, n=20), cold acclimated (CA, n=20) and exercise trained (ET, n=20) groups. ET rats were trained by running on a treadmill 1 hour daily, 6 days a week for a period of 8 weeks at about 35 m/min. Analysis of the urinary catecholamine metabolites, VMA and HVA, was performed by a high performance liquid chromatography. It was shown that when the animals underwent a cold exposure test at 5°C for 1 hour, oxygen consumptions ( VO₂) in WA rats increased only slightly, whereas VO₂ in ET and CA rats increased very markedly. It was found that increases of the urinary VMA and HVA excretions by the treadmill exercise in ET rats was significantly lower than that obtained by cold exposure in CA rats. The rise in colonic temperature was significantly 3-fold higher with exercise running for 1 hour in ET rats than with chronic cold exposure in CA rats. Exercise training showed to suppress brown adipose tissue's weight (BAT) . It has been suggested exercise training-induced hyperthermia and norepinephrine (NE) secretion would be an antagonistic adaptation of BAT nonshivering thermogenesis. In conclusion, the present study indicates that the improved capacity for cold-induced thermogenesis in the ET group may not be ascribed to enhanced nonshivering thermogenic response to NE.