Diagnosis of cyanide intoxication by measurement of cytochrome c oxidase activity

Cytochrome c oxidase (CCO), a mitochondrial enzyme, is inactivated by cyani de or carbon monoxide (CO) intoxication. We measured CCO activity, in the m ajor organs of the rat at various times after death caused by cyanide intox ication. Tissue samples were homogenized, and the CCO activity in the mitoc hondrial fraction was measured using ferrous cytochrome c as the substrate. The CCO activity inhibition was highest in the brain, although the cyanide concentration was lowest level. As a result of this and the clinical sympt oms displayed, we consider the brain to be the primary organ of cyanide int oxication. As cyanide is highly toxic to humans, in small amounts and many patients and victims have already had some medical care, it is difficult to detect cyanide in criminal investigations. The CCO activities in various o rgans remained significantly low for 2 days after the cyanide intoxication, suggesting that the diagnosis may be possible by measuring not only the cy anide concentration but also the CCO activity. (C) 2001 Elsevier Science Ir eland Ltd. All rights reserved.