Changes of lipid peroxidation parameters in dogs with alloxan diabetes

Diabetic human patients and laboratory animals show abnormalities which can be observed also in enhanced lipid peroxidation (LPO) induced in vitro. It seemed to be necessary to demonstrate the presence of these processes also in dogs with experimentally induced alloxan diabetes. In a 5-day experiment, five 1 to 5-year-old dogs of mixed sex were examined. Blood samples were taken before the intravenous administration of 60 mg alloxan/kg body mass and then daily for a period of 5 days. After the administration of alloxan, the dogs became depressed and lost their appetite. Their urine contained varying concentrations of glucose detectable with a test strip. As compared to the physiological values, blood glucose concentration increased considerably throughout. Alanine aminotransferase (ALT) enzyme activity underwent an 8-fold increase by the 24th hour; subsequently, it remained practically unaltered. The malonyldialdehyde (MDA) concentration of red blood cell (RBC) haemolysate also rose with respect to the basal values. Glutathione-peroxidase (GSH-Px) activity increased only transiently, up to the second day of the experiment; subsequently, its activity dropped below the basal values. Similar changes were found in catalase activity, while the activity changes of superoxide dismutase (SOD) were identical in tendency to the above ones; in fact, it hardly showed any alterations. Besides the severe pancreatic and liver damage caused by alloxan, increased MDA production in the RBC haemolysate indicated enhanced peroxidation of polyunsaturated fatty acids, i.e. intensification of the LPO processes. The increase of GSH-Px and catalase activity, followed by their decrease was suggestive of changes in the enzymatic defence mechanism acting against free radicals.