Effects of 6-hydroxydopamine on oxidative phosphorylation of mitochondria from rat striatum, cortex, and liver

The catecholamine neurotoxin 6-hydroxydopamine (6-OHDA) has been used to produce cardiac chemical sympathectomy as well as a model of parkinsonism. Several mechanisms have been proposed to explain its cytotoxicity, including the productions of quinones, hydrogen peroxide, and free radicals by autooxidation and the uncoupling of mitochondrial oxidative phosphorylation. We have observed that 6-OHDA at a concentration of 0.05 mM rapidly consumes oxygen from the mitochondrial incubation medium but does not affect oxidative phosphorylation in the mitochondria from rat striatum, cortex, and liver. At the higher concentration of 0.5 mM, 6-OHDA consumes all of the available oxygen from the incubation medium. Mitochondria exposed to this concentration of 6-OHDA show decreases in the respiratory control ratio and adenosine triphosphate synthesis as measured by the consumption ratio of ADP to oxygen. Thus, only the higher (0.5 mM) concentration of 6-OHDA, which produces anoxia in vitro, also causes mitochondrial damage.