Cadmium chloride prevents the rise in rat brown adipose tissue mitochondrial respiration in response to acute cold stress

In mammals, cold exposure produces a sharp rise in brown adipose tissue (BAT) thermogenesis. In this study, the effects of cadmium on BAT mitochondrial oxygen consumption in response to cold were examined in normal and triiodothyronine (T sub(3))-treated and untreated hypothyroid rats. All treated rats were injected with a single dose of Cd at 107.8 mu g/110 g body weight. Results showed that untreated, cold-exposed normal rats exhibited a twofold rise in O sub(2) consumption, whereas the rise in T sub(3)-treated rats was not significant. Increases in BAT O sub(2) consumption after cold exposure were severely diminished after the administration of Cd. The normal rats were unable to increase O sub(2) consumption in response to cold, which correlated with a nine-fold increase in BAT Cd content. The implicated mechanism was via Cd inhibition of BAT thyroxine-to-T sub(3) conversion, but Cd may also effect the activities of cytochrome oxidase and mitochondrial alpha -glycerophosphate dehydrogenase activities.