Regional and Subcellular Distribution of Cyanide Metabolizing Enzymes in the Central Nervous System

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Abstract
Activities of cyanide metabolizing enzymes were measured in various subcellular fractions and regions in the central nervous system. Brain rhodanese and liver β‐mercaptopyruvate sulfurtransferase showed a slight decrease in activity after death. The activity of β‐mercaptopyruvate sulfurtransferase was negligible in the rat brain, compared with that of rhodanese. A small amount of thiocyanate was produced from cyanide and β‐mercaptopyruvate in the human brain, probably due to contamination with red blood cells. Rhodanese activity was widely distributed in all the areas of nervous tissue examined. In the rat the olfactory bulb showed the highest rhodanese activity, and high activity was also observed in the thalamus, septum, hippocampus, and dorsal part of the midbrain. Rhodanese activity was low in various parts of the cerebral cortex. The distribution pattern of rhodanese in post‐mortem human brain was essentially similar to that in rat brain. The thalamus, amygdala, centrum semiovale, colliculus superior, and cerebellar cortex showed high rhodanese activity in the human brain. Rhodanese activity was detected in the spinal cord. Anterior horn showed the highest rhodanese activity in the cervical, thoracic, and lumbar cord. Most rhodanese activity in the rat brain was recovered in the mitochondrial fraction with the highest specific activity. Rhodanese activity was lower in spinal cords obtained from autopsied cases with amyotrophic lateral sclerosis than in those of control subjects. A significant decrease in rhodanese was observed in the posterior column of the cervical or thoracic cord, but the activity in the anterior horn did not differ significantly between the two groups.