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 exposure on the mRNA expression and immunoreactivity of superoxide dismutase (SOD) isoenzymes [Mn-SOD, Cu,Zn-SOD, and extracellular-SOD (EC-SOD)] in different tissues from lean and obese (ob/ob) mice at 10 months of age. The animals were kept at 10 degrees C for 3 h, with the colonic temperature in obese mice declining progressively during the cold stress, but not in lean mice, probably 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 significant decline in Cu,Zn-SOD in kidney and in Mn-SOD and EC-SOD in white adipose tissue (WAT), as well as in all SOD isoenzymes in lung and BAT. In obese mice, the mRNA level of Mn-SOD in heart and gastrocnemius muscle was significantly decreased following the cold exposure, whereas that of EC-SOD in testes was significantly increased. These changes, however, were not always accompanied by those in the corresponding protein levels; for example, the significant decreases in the expression of mRNAs for the three SOD isoenzymes in lung and BAT from lean mice did not result in any changes in the respective 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 marked decrease in colonic temperature, acute exposure to cold has less effect on SOD isoenzymes in obese mice as compared with those in normal lean siblings.