New reactive oxidizing species causes formation of carbon-centered radical adducts in organic extracts of blood following liver transplantation

Effect of intermittent hepatic pedicle clamping on free radical generation in the rat liver

BACKGROUND

Intermittent hepatic pedicle clamping is thought to cause less hepatic reperfusion injury compared with continuous clamping. The mechanisms underlying this difference are unknown. We examined the relationship between intermittent ischemia/reperfusion and the production of free radicals using electron spin resonance spectrometry.

METHODS

Alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone was administered to rats as a spin trap agent. Continuous clamping (15, 30, or 60 minutes) or intermittent clamping (four cycles of 15-minute ischemia and 5 or 15 minutes of reperfusion) of hepatic pedicle was carried out. After reperfusion, free radical production in the liver was measured by an electron spin resonance spectrometer, and the level of hepatic injury was evaluated by measuring liver enzyme.

RESULTS

Longer periods of ischemia increased free radical production after reperfusion. There was no significant increase in free radical production or liver enzymes when the duration of ischemia was 15 minutes. Free radical production and liver damage were significantly less severe in intermittent pedicle clamping than in continuous clamping for 60 minutes, especially when the duration of the reperfusion between four cycles of ischemia was 15 minutes.

CONCLUSIONS

These results indicate that intermittent pedicle clamping lessens free radical production when compared with continuous clamping, although many free radicals are produced.

MDL 74,180 reduces cerebral infarction and free radical concentrations in rats subjected to ischaemia and reperfusion

The protective effect of MDL 74,180 (2,3-dihydro-2,2,4,6, 7-pentamethyl-3-(4-methylpiperazino)-methyl-1-benzofuran-5-ol dihydrochloride) and alpha-tocopherol analogue free radical scavenger, against cerebral ischaemia and reperfusion in conscious rats has been demonstrated. Tissue damage following middle cerebral artery occlusion (2 h) and reperfusion (8 days) was decreased by MDL 74,180 (0.1 and 1.0 mg/kg per h) infusion beginning 15 min before the onset of reperfusion and continuing for 2 h into the reperfusion period, in a dose-related manner. Nitroxide radical adducts, characterized and quantified by electron spin resonance spectroscopy, were formed on the addition of spin traps to homogenized rat brain tissue previously subjected to global ischaemia and reperfusion. The primary oxidative chain free radicals form diamagnetic intermediates whose slow homolytic decomposition subsequently yields the observed stable spin adducts. Infusion of MDL 74,180 (1-10 mg/kg per h) beginning 15 min before the induction of global cerebral ischaemia (20 min) until the end of reperfusion (5 min), led to a dose-dependent reduction in the final concentration of spin adducts.

The effects of alpha-phenyl-tert-butyl nitrone (PBN) on copper-induced rat fulminant hepatitis with jaundice

In the present study we demonstrated the protective effects of the spin-trapping agent alpha-phenyl-tert-butyl nitrone (PBN) against fulminant hepatitis with jaundice in LEC rats. In LEC rats an excess amount of copper is accumulated in the liver and causes hepatitis with severe jaundice. PBN was subcutaneously administered every 2 d at the concentration of 128 mg/kg, beginning with 13-week-old rats and continuing for 17 weeks. PBN prevented the loss of body weight, reduced death rate, and suppressed the increase in GTP and GOT values reflecting hepatic cell destruction. Ocular inspection also confirmed the suppressive effects of PBN on jaundice. In parallel with these phenomena, the amounts of thiobarbituric acid-reactive substances (TBARS) in livers of PBN-administered rats were found to be lower than those of non-PBN-administered rats. Little histological changes were observed in PBN-administered rats in comparison with non-PBN-administered rats. The protective effect of PBN on the formation of oxidative damage in liver DNA was observed but not so remarkable as that on lipid peroxidation. From these results, it was concluded that PBN had the liver-protective effects against fulminant hepatitis with jaundice. This suggested that free radicals play an important role in abnormally accumulated copper-induced liver injury and that PBN potentially has therapeutic value for the treatment of hepatitis.