Neuronal Degeneration in the Brain of Brindled Mice: Combined Histochemical and Biochemical Studies on Cytochrome Oxidase and Superoxide Dismutase Activities

Abstract

In an effort to elucidate the mechanism(s) responsible for the brain degeneration in Menkes' disease, the authors determined the activities of two copper‐containing enzymes, cytochrome oxidase and superoxide dismutase in brains of brindled hemizygous mice (BM) before and after the injection of 10 mUg/g of cupric chloride (CuCI2) on postnatal day 7. Combined use was made of histochemical and biochemical methods. Histochemical staining for brain cytochrome oxidase in untreated BM was greatly decreased, and by biochemical analysis found to be approximately 30% of the normal level. By contrast, the activity levels in BM surviving for 6 to 12 months following the injection were the same as those in the normal control animals. Similar results were obtained for superoxide dismutase. Sequential chronological assays revealed that brain cytochrome oxidase activity of copper (Cu)‐treated BM gradually increased as a function of age, reaching normal levels by the end of 25 weeks. These findings were in concordance with the normal morphological features of the animals. However, the brain Cu content of the Cu‐treated BM showed only a slight increase; normal concentrations were not reached even by 26 months post‐treatment, when their Cu levels were 55.4% those of the normal controls. Taken together, these results may explain the mechanism of brain degeneration and efficacy of Cu therapy in Menkes' disease, and may offer hope for treating this inherited disorder. However, before it can be put into practice, it would be important to devise effective means for the safe delivery of Cu to an affected human fetus before it sustains irreversible brain damage.