Decreased hippocampal metabolic activity in Alzheimer patients is not reflected in the immunoreactivity of cytochrome oxidase subunits.

In the present study we have compared histochemically determined cytochrome oxidase activity with the levels of immunocytochemically stained cytochrome oxidase subunits (CO II and CO IV) and ATP synthase in the human hippocampus in relation with Alzheimer's disease. Cytochrome oxidase activity was significantly reduced in all hippocampal areas of Alzheimer patients. The protein levels of subunits II and IV were not different between control subjects and Alzheimer patients. Additionally, it was observed that the active cytochrome oxidase is evenly distributed over both cell bodies and neuropil, while a relatively large pool of inactive enzyme or precursors is limited to the neuronal somata. Further, in Alzheimer patients the CO IV immunoreactivity decreased with age, whereas in control subjects it increased with age. Our results suggest that the assembly of cytochrome oxidase or the processing of its subunits may be impaired. Copyright 2000 Academic Press.