Environmental induction models for the investigation of activity: changes in glutathione peroxidase, a crucial factor of the antioxidant defence.

Glutathione peroxidase enzyme superfamily plays significant role in the elimination of reactive oxygen free radicals in the animals. Many characteristics of these proteins have been revealed already, but their regulation is still not known. Several data suggest that some environmental factors have certain regulatory effect, while others propose strict genetic regulation. In this report we present four different environmental induction models in which New Zealand white rabbits were used as experimental animals. In three models, free radical load of different origin, lipidperoxide load, application of a glutathione depletor or a prooxidant agent, was introduced. Beside these negative models a positive model was also constructed in which additive selenium was supplied. Glutathione peroxidase activity was measured in blood serum, erythrocyte haemolysate and liver. Reduced glutathione, and malondialdehyde concentration in the liver were also determined. According to the results, the established models are capable for analysing the enzyme activity x environmental interactions.

Polymorphism of the rabbit kappa kasein gene and its influence on performance traits.

The rabbit kappa-casein encoding gene has previously been shown to possess two alleles. The two alleles do not differ in their coding region and in the accumulation levels of mRNA. However they differ greatly with respect to their intronic regions. The rearranged regions in the first and fourth introns were found to be inverse and complementary LINE sequences. The A allele was found to be more frequent in different European breeds. Correlation of the kappa-casein genotype with the breeding capacity in a New Zealand White rabbit stock has been examined.

Oxidative stress induced by bloodless limb surgery on humans.

Measure of oxidative stress were studied in blood samples from 10 patients undergoing bloodless lower limb surgery. Ischaemia induced a significant increase in plasma hypoxanthine concentration and xanthine oxidase activity both in the operated leg and in the systemic circulation. Five minutes after reperfusion, ratio of xanthine oxidase/total xanthine oxidase and dehydrogenase activities rose moderately, whereas at 20 min xanthine oxidase accounted for all xanthine oxidoreductase activity in the systemic circulation. A significant increase in blood glutathione redox ratio, enhanced oxidation of haemoglobin to methaemoglobin and rise in plasma haemoglobin concentration were present only in the operated limb. Thus, although the level of the potential free radical generators rose significantly both locally and in the systemic circulation, oxidative stress, as indicated by blood glutathione and erythrocyte injuries, remained limited to the reperfused leg.

Effect of lipid peroxide loading on lipid peroxidation and on the glutathione and cytochrome systems in rabbits.

New Zealand White rabbits (6 males and 6 females) were fed a diet of high lipid peroxide content (peroxide value: 249.05 meq/kg fat) for 21 days. Twelve rabbits served as controls (peroxide value: 40.3 meq/kg fat). The lipid peroxide loading did not cause clinical signs. The rate of lipid peroxidation, as measured on the basis of thiobarbituric acid reactive substances (TBARS), was significantly (P < 0.05) higher in all of the investigated tissues, in the following order: liver > red blood cells (RBC) > blood plasma. Reduced and oxidised glutathione content was higher in the blood plasma (P < 0.01) and liver (P < 0.001) of rabbits exposed to the peroxide load. Lipid peroxide loading decreased the activity of glutathione peroxidase in the blood plasma, RBC haemolysate and liver and that of glutathione reductase in the liver. The amount of cytochrome P450 (both CO- and metyrapone-reduced) and the activity of cytochrome c (P450) oxidoreductase in the microsomal fraction of the liver homogenate were also lower in the group exposed to lipid peroxide load. Subchronic alimentary lipid peroxide loading in the presence of sufficiently high levels of antioxidants in the complete feed was found to increase the rate of lipid peroxidation and markedly lower the activities of both the glutathione and xenobiotic transforming enzyme systems without causing any clinical signs of toxicity.