Akademik Veri Yönetim Sistemi
Cancer Research Therapy and Control, cilt.5, sa.3, ss.195-201, 1998 (Scopus)
Activities of some DNA turn-over enzymes, namely adenosine deaminase (ADA), 5'nucleotidase (5'NT), guanase (GUA), xanthine oxidase (XO), xanthine dehidrogenase (XD), and hypoxanthine-guanine phosphoribosyl transferase (HGPRT) and those of free radical defense enzymes, namely superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were measured in cancerous and non-cancerous human liver tissues. Levels of peroxidation indexes (PI), namely thiobarbituric acid-reagent substances (TBARS) and conjugated diens (CD) were also measured in the liver tissues. Of the DNA turn-over enzymes, ADA, XO and HGPRT activities in cancerous tissues were found higher, 5'NT unchanged, GUA and XD decreased compared with those of non-cancerous tissues. All of the free radical defense enzymes were found inhibited or repressed in the cancerous tissues. It has been found that the level of TBARS decreased but those of CD unchanged in the cancerous tissues. Correlation analysis results showed that enzymatic relations between enzyme activities were disordered in the cancerous tissues and mostly negative relations existed between the activities of the DNA turn-over and free radical defense enzymes. Results suggested that DNA turn-over was accelerated and that the free radical defense system was depressed in human liver cancers. Although XO system, the main radical producing mechanism in most of the cells was activated and the enzymatic antioxidant defense system was suppressed, no peroxidation reactions happened in the cancerous tissues. This indicates that cancerous liver tissues have strong, non-enzymatic, antioxidant defense mechanisms capable of eliminating free radicals and preventing peroxidation reactions.