DYSFUNCTION OF MOUSE-LIVER MITOCHONDRIA INDUCED BY 2,2'-AZOBIS-(2-AMIDINOPROPANE) DIHYDROCHLORIDE, A RADICAL INITIATOR, IN-VITRO AND IN-VIVO

Mouse liver mitochondria were uncoupled in a time dependent by intrape ritoneal injection of a radical initiator, 2,2'-azobis-(2-amidinopropa ne) dihydrochloride (AAPH) (100 mg/kg). State 3 respiration, ADP/O rat io and respiratory control ratio (RCR) were decreased 30 min after inj ection but there was no effect on state 4 respiration. Lipid peroxidat ion was increased and oxidative phosphorylation was uncoupled at one h r after drug injection but gradually recovered to normal levels after 14 hr in vivo. State 3 respiration, RCR and ADP/O ratio but not state 4 respiration of isolated mouse mitochondria were inhibited by short t erm incubation with AAPH in vitro. This inhibitory action was concentr ation dependent (ID50 = 5 mM) but was not prevented by alpha-tocophero l. AAPH had no effect on electron transport or the membrane potential of these isolated mitochondria. However, mitochondria were uncoupled v ia lipid peroxidation and swelling by long term incubation with AAPH. These inhibitory effects of AAPH were reduced by its spontaneous degra dation not only in vitro but also in vivo. Thus AAPH induces mitochond rial dysfunction by direct action in the early period of treatment and free radicals produced from AAPH mediate mitochondrial swelling via l ipid peroxidation in the late period. From these findings, it is concl uded that mitochondrial phosphorylation plays an important role in the pathogenesis of liver injury induced by AAPH and that radicals genera ted by AAPH might be a source of liver injury and mitochondrial dysfun ction in vivo.