Investigation of catalytic properties of glutathione reductase obtained by chromatographic methods from the liver of rats with paracetamol-induced liver damage upon administration of 6-hydroxy-2,2,2,4-trimethyl-1,2-dihydroquinoline

Abstract

The aim of the present study was to analyze some catalytic and regulatory properties of the enzyme preparation of glutathione reductase (GR, EC 1.6.4.2.) obtained from rat liver using gel filtration and ion exchange chromatography under conditions of paracetamol-induced liver injury (PILI) and administration of 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline (DHQ). Laboratory animals (Rattus norvegicus rats of the Wistar line) were divided into 3 groups. The animals of the control group were orally administered vaseline oil. The second group consisted of rats with PILI induced by a single oral administration of paracetamol at a dose of 1000 mg/kg body weight dissolved in 1 cm3 of vaseline oil. Animals of the third group were modeled by PILI and orally administered with DHQ at a dose of 50 mg per 1 kg body weight dissolved in 1 cm3 of 1% starch, 1 hour and 12 hours after paracetamol administration. Liver and serum were collected 24 hours after paracetamol administration. GR activity was measured on a spectrophotometer at 340 nm wavelength. The enzyme was purified from rat liver by ammonium sulfate fractionation, gel filtration through Sephadex G-25, and ion exchange chromatography on DEAE-cellulose. The total amount of protein in the samples was measured using the BCA protein assay kit. GR was obtained from the liver of rats treated with DHQ on the background of PILI with a 32-fold purification degree. Using the method of double inverse Lineweaver-Burk coordinates it was shown that administration of DHQ to rats was accompanied by a decrease in the affinity of the enzyme for NADPH, as compared to the indicators at pathology. The introduction of isocitrate into the spectrophotometric medium resulted in a less pronounced increase in the activity of GR from the liver of animals treated with DHQ on the background of PILI, compared to the second group of rats. The enzyme from the liver of animals of the third group was characterized by a more significant decrease in activity when glucose-6-phosphate was introduced into the reaction medium. Citrate had a less pronounced regulatory effect on GR from the liver of rats treated with DHQ on the background of pathology, relative to the indicators of animals with PILI. The changes in enzyme properties demonstrated may be due to conformational changes in the molecule resulting from the inhibition effect of DHQ on the intensity of free radical-induced oxidation, which develops against the background of the toxic effect of paracetamol metabolites.