Alterations in the activities of DNA topoisomerase enzymes and O6-methylguanine-DNA-methyltransferase in septic rat liver.

To understand the genomic changes contributing to the various metabolic derangements in sepsis and septic shock, we measured the activities of the following liver enzymes intimately associated with DNA function: (1) DNA topoisomerases I and II (topo I and topo II) controlling DNA conformation in mammalian nuclei, and (2) O6-methylguanine-DNA-methyltransferase (MT) capable of removing the methyl groups from the O6-position of guanine in DNA. We found that in septic rat livers the specific activities (units/mg protein) of topo II and MT were elevated by 1.4- and 1.6-fold, respectively, over the sham-operated controls (P less than 0.001). There was no significant difference in topo I activity. We believe that peritonitis sepsis alters topo II levels modulating the selective pretranscriptional changes in chromatin and that MT functions as a cellular stress protein.