No abstract

Hypothermic oscillating oxygenated perfusion led to the elevated energy charge during preservation and led to reduced oxygen radical formation as well as less lipid peroxidation during reperfusion, in contrast to cold stored livers and nonpreserved livers. This suggests a correlation between the energy charge before reperfusion and oxygen radical formation as well as liver injury at reperfusion.

Background/Aim: α-Lipoic (LA) acid pretreatment has previously been described to reduce ischemia/reperfusion injury (IRI) after warm liver ischemia, whereas glycine pretreatment has been shown to be protective mostly in models of cold hepatic ischemia. The aim of this study was to determine whether glycine decreases IRI after warm hepatic ischemia. Furthermore we investigated whether doses of LA other than those used previously are also protective against IRI after warm hepatic ischemia. Methods: Selective liver ischemia was maintained over a period of 90 min. In long-term as well as short-term experiments we studied IRI in several groups comparing animal survival as the pivotal endpoint. Results: Animal survival was improved by glycine and 5,000 µmol LA, whereas all animals died within 3 days after pretreatment with 50 µmol LA. In the glycine group we observed a tendency towards decreased apoptosis-related cell death measured by the activity of caspase-3 in liver tissue and the percentage of TUNEL-positive hepatocytes in comparison to the untreated group. Serum α-glutathione S-transferase, lipid peroxidation, and caspase-3 activity as well as the percentage of TUNEL-positive hepatocytes and the percentage of liver necrosis were only significantly decreased by 5,000 µmol LA pretreatment. Liver tissue levels of tumor necrosis factor (TNF)α were reduced only in the glycine group whereas TNFα was increased in the untreated as well as the LA group. Levels of TNFα mRNA were upregulated in both the glycine- and LA-pretreated groups. Conclusion: Our data show that increased animal survival by glycine was accompanied by a reduced TNFα content in liver tissue. Protection by glycine is likely to result from a reduction in adverse TNFα effects. Administration of high-dose LA on the other hand led to a significant reduction in necrosis- and apoptosis-related cell death in IRI of the liver without a reduction in liver TNFα.

No abstract

The light-induced enhancement of the 7-ethoxycoumarin-O-deethylase activity was measured in a reconstituted system, consisting of the enzyme P-450PB-B and the NADPH -cytochrome P-450 reductase. The relative increase of the activity was about 15%. It is shown that the product release process is accelerated by light. The phases of the catalytic cycle of 2 x 1012 protein complexes were locked by periodic application of light pulses (0.1 s duration, 1.32 s repetition time, and 390 -470 nm, 0.27 joule/nmol P-450). More than 80% of the active reconstituted enzyme complexes (= “molecular machines”) worked in phase after a few light pulses. The phase relation continued even after switching off the light pulses. The catalytic cycle time was 1.54 s, giving a turnover number of 39 min-1. The turnover number, as determined from the enzyme activity under optimum conditions, was 39 min-1. Due to the dissociation constant of the P-450PB-B:NADPH - P-450 reductase complexes [3] only 24% of the proteins were in the active (= working) state under the conditions used. The lifetime of this complexes is larger than 6 s since more than 4 cycles of the free running enzyme can be observed. This is the first report, that all catalytic active complexes in the test tube can be synchronized by an external light source, if the right repetition time of the pulses is chosen, so that all these “molecular machines” work in phase.