Biochemical changes in the rat lung and liver following intratracheal instillation of cadmium oxide

Acute biochemical changes in the rat lung and liver following intratracheal instillation of cadmium oxide (CdO) were observed at a dose of 5 micrograms Cd/rat to investigate the defense mechanism to Cd intoxication via airway. In the lung metallothionein (MT) was induced, reaching a maximum at 2 days. A slight increase in reduced glutathione (GSH) concentration was observed at 4 days. The activity of glucose-6-phosphate dehydrogenase (G6PDH) was increased and superoxide dismutase (SOD) activity was slightly decreased, but glutathione peroxidase (GPx) and glutathione reductase (GR) activities were not changed. These observations suggested that MT played a key role in detoxification of instilled CdO, but that the antioxidant enzymes had a minimal role. In the liver MT and GSH concentrations were diminished 7 h after instillation and returned to their control levels. Hepatic GPx activity was increased 1 day after instillation and the significantly elevated level lasted up to 7 days, while hepatic GR activity was decreased. These hepatic biochemical changes are suggested to be due to the secondary effects of the lung injury.