STUDIES OF MITOCHONDRIA IN OXIDATIVE EMBRYOTOXICITY

While the limb bud and brain of the rat develop abnormally in response to transient uteroplacental hypoperfusion during late gestation, the heart appears to be protected. These malformations have been associate d with the generation of reactive oxygen species (ROS). Studies were d esigned to examine superoxide generation by mitochondrial electron tra nsport particles (ETP) from adult and conceptal tissues and to investi gate characteristics that could be responsible for heightened concentr ations of ROS in sensitive tissues. Parameters investigated included N ADH oxidase and cytochrome c oxidase activities, cytochrome content, a nd superoxide dismutase activity. NADH oxidase activities were signifi cantly lower in sensitive tissues that also developed the highest conc entrations of superoxide. Because ETP from adult CNS also had low NADH oxidase activity but did not show increased concentrations of superox ide, inhibition of electron transport did not adequately account for i ncreased ROS concentrations. The reduced NADH oxidase activity of sens itive tissues could not be caused by inhibition at the cytochrome c ox idase region since this latter activity equaled or exceeded the former in all instances. No significant differences were found in the cytoch rome contents of different tissues. There was significantly less super oxide dismutase activity in homogenates prepared from either of the tw o sensitive conceptal tissues compared with those from insensitive con ceptal or adult tissues. These studies confirm the presence of heighte ned concentrations of superoxide anion radical in ETP from teratogenic ally sensitive tissues and suggest that these concentrations may resul t primarily from decreased activity of superoxide dismutase(s) in thos e tissues. Superoxide anion radical could therefore be available to pa rticipate in the generation of the more toxic oxidant species such as the hydroxyl radical. (C) 1995 Wiley-Liss, Inc.