Effects of acute cold stress on mRNA expression and immunoreactivity of three superoxide dismutase isoenzymes in genetically obese mice

The aim of this study was to investigate the influence of acute cold exposu re on the mRNA expression and immunoreactivity of superoxide dismutase (SOD ) isoenzymes [Mn-SOD, Cu,Zn-SOD, and extracellular-SOD (EC-SOD)] in differe nt tissues from lean and obese (ob/ob) mice at 10 months of age. The animal s were kept at 10 degreesC for 3 h, with the colonic temperature in obese m ice declining progressively during the cold stress, but not in lean mice, p robably because of a strong tendency to atrophy of the brown adipose tissue (BAT) in obese mice. In the expression of mRNAs for lean mice, acute cold exposure led to a significant increase only in Mn-SOD in testes, but a sign ificant decline in Cu,Zn-SOD in kidney and in Mn-SOD and EC-SOD in white ad ipose tissue (WAT). as well as in all SOD isoenzymes in lung and BAT. In ob ese mice, the mRNA level of Mn-SOD in heart and gastrocnemius muscle was si gnificantly decreased following the cold exposure, whereas that of EC-SOD i n testes was significantly increased. These changes, however, were not alwa ys accompanied by those in the corresponding protein levels, for example, t he significant decreases in the expression of mRNAs for the three SOD isoen zymes in lung and BAT from lean mice did not result in any changes in the r espective isoenzyme protein levels. These results suggest that, except For testes, a cold-exposure period of 3 h down-regulates SOD isoenzymes at the transcriptional process especially in lean mice, but is not long enough to induce their protein synthesis. It seems likely, thus, that, despite a mark ed decrease in colonic temperature, acute exposure to cold has less effect on SOD isoenzymes in obese mice as compared with those in normal lean sibli ngs.