EFFECT OF EPIGALLOCATECHIN-3- GALLATE AND QUERCETIN ON THE PRODUCTION OF REACTIVE OXYGEN AND NITROGEN SPECIES IN LIVER OF RATS EXPOSED TO ROUND-THE-CLOCK LIGHT AND KEPT ON CARBOHYDRATELIPID DIET

Abstract

The purpose of this study is to investigate the effects of bioflavonoids, epigallocatechin-3-gallate (EGCG) and quercetin, on the production of reactive oxygen and nitrogen species in the liver of rats under round-the-clock light exposure with an intensity of 1500 lux for 30 days while being kept on carbohydrate-lipid diet (20% fructose solution and appropriate food) for 60 days. In the liver tissues, the rate of the superoxide anion production by NADPH-dependent electron transport chains (microsomal monooxygenases and constitutive uncoupled NO synthases) increased by 1.93 times, by the mitochondrial respiratory chain by 1.89 times, and it was doubled by leukocyte NADPH-oxidase. The total activity of NO synthase was increased by 2.35 times, the activity of its inducible isoform increased by 2.57 times, and the concentration of alkali and alkaline earth metals peroxynitrites elevated by 1.68 times. Administration of bioflavonoids-epigallocatechin-3-gallate and quercetinsignificantly restrained the rate of superoxide anion production in the liver tissues by microsomal monooxygenases and NO synthase by 39.1 and 40.1%, by the mitochondrial respiratory chain by 37.2 and 34.4%, by leukocyte NADPH-oxidase by 35.0 and 32.1%, respectively. Epigallocatechin-3-gallate and quercetin inhibited the total activity of NO-synthase by 46.7 and 36.2%, the activity of its inducible isoform by 49.6 and 39,0%, increased the activity of the constitutive isoenzyme NO-synthase by 2.9 times and its coupling index by 4.5 and 4.7 times. Additionally, administration of these bioflavonoids lowered the concentration of peroxynitrites of alkali and alkaline earth metals by 30.5 and 34.3% compared to the respective values obtained in the group of rats, which did not receive the bioflavonoids, but were exposed to light and carbohydrate-lipid-rich diet. We suggest that epigallocatechin3-gallate and quercetin in the above experimental conditions are effective means to restrain the formation of reactive oxygen and nitrogen species in the liver tissue.