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 cytochrom e oxidase subunits (CO II and CO IV) and ATP synthase in the human hippocam pus in relation with Alzheimer's disease. Cytochrome oxidase activity was s ignificantly reduced in all hippocampal areas of Alzheimer patients. The pr otein levels of subunits II and IV were not different between control subje cts and Alzheimer patients. Additionally, it was observed that the active c ytochrome 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 immunoreac tivity decreased with age, whereas in control subjects it increased with ag e. Our results suggest that the assembly of cytochrome oxidase or the proce ssing of its subunits may be impaired. (C) 2000 Academic Press.