Reduction kinetics and content of cytochrome P-450 by application of dual wavelength techniques to hemoglobin-free perfused rat liver

Hemoperfusion, rate of oxygen consumption and redox levels of mitochondrial cytochrome c (+c1) in liver in situ of anesthetized rat measured by reflectance spectrophotometry

Utilizing reflectance spectrophotometry, hemoperfusion, rate of oxygen consumption and redox level of mitochondrial cytochrome c (+c1) in livers in situ of anesthetized rats were measured. The transition to the anoxic state was induced by raising the pressure on the liver surface to more than the hepatic blood pressure by pressing with the tip of the optical guide of the reflectance spectrophotometer. During this transition, the average oxygen saturation of hemoglobin in the liver in situ decreased linearly with time until it became 10--20% of the total. This was followed by reduction of mitochondrial cytochrome c (+c1), which reached completion in 10--20 s. The measured O2 consumption rate remained constant until the percentage of oxyhemoglobin in situ decreased to a critical level. There was then a decrease in the rate of O2 consumption which was accompanied by a progressive reduction of cytochrome c (+c1). It was shown that amounts of hemoglobin and mitochondrial respiratory chain cytochromes in the liver in situ could be measured non-invasively and could provide important signals for vital cellular functions. The changes in hemoperfusion and rate of O2 consumption of the liver in situ following ethanol ingestion were also shown in rats, and are briefly discussed with respect to possible application of this method to study the pathophysiology of tissues.

Electron paramagnetic resonance spectra of catalase in mammalian tissues

The relatively small number of paramagnetic species and the high concentration of catalase in mammalian liver and blood make it possible to directly study this enzyme in frozen whole tissue. The EPR spectra of catalase are dependent on the heme environment and in human blood only catalase A, gxy = 6.48, 5.36 is observed whereas in liver a second spectrum, catalase B, gxy = 6.80, 5.07 can also be seen. Using rapid freeze techniques it has been shown that in rat liver catalase A corresponds to the in vivo steady state and that after death this is largely converted into catalase B. Data from the perfusion of rat livers with oxygenated and deoxygenated blood and dextran solutions together with results from in vitro studies of catalase are interpreted as indicating that catalase B results from the interaction of catalase with an organic acid, most probably formic acid, that the acid is a peroxidative substrate for catalase in vivo and that peroxidation of the acid is not the major role for catalase in rat liver. Catalase binding with other small molecules in intact liver has been demonstrated by perfusion with nitrite-containing dextrans and by intraperitoneal injection of 3-amino-1,2,4-triazole.

Mixed function oxidase and ethanol metabolism in perfused rat liver

Oxidation-reduction changes of cytochrome P-450 and oxygen consumption were measured in isolated perfused livers from normal and phenobarbital-treated rats. Phenobarbital treatment markedly increased the aminopyrine-induced reduction of cytochrome P-450, but ethanol did not cause any redox changes of this cytochrome. It was concluded that the microsomal ethanol-oxidizing system has an insignificant role in the metabolism of ethanol in intact liver.