Unaltered cytochrome oxidase, glutamate dehydrogenase and glutaminase activities in platelets from patients with sporadic amyotrophic lateral sclerosis--a study of potential pathogenetic mechanisms in neurodegenerative diseases.

Sporadic Amyotrophic Lateral Sclerosis (SALS) is a fatal neurologic disease characterized by degeneration of motor neurons in the spinal cord, brainstem and cortex. While familial cases of ALS exist, the sporadic form accounts for the majority of adult-onset cases. It has been hypothesized that the neurodegenerative mechanisms underlying SALS might arise from glutamate-mediated excitotoxicity and mitochondrial dysfunction. Studies on autopsied SALS spinal cord and brain have reported decreased cytochrome oxidase activity, decreased astrocytic glutamate-transporter protein, and alterations of glutamate levels and glutamate metabolizing enzyme activities. We conjectured that if alterations in glutamate metabolism and cytochrome oxidase activity occur in the SALS central nervous system these alterations may also be manifested in peripheral tissues such as platelets in living SALS patients. In this study we compared the activities of cytochrome oxidase, citrate synthase, glutamate dehydrogenase and glutaminase in platelets from SALS and control subjects. We found that there were no differences in any of the enzyme activities measured between the two groups. Our data argue against generalized ubiquitous biochemical alterations of these enzymes in SALS patients.