RELEASE OF FREE, REDOX-ACTIVE IRON IN THE LIVER AND DNA OXIDATIVE DAMAGE FOLLOWING PHENYLHYDRAZINE INTOXICATION

Following the subchronic intoxication of rats with phenylhydrazine, re sulting in marked anemia, reticulocytosis, methemoglobinemia and incre ased hemocatheresis, the hepatic content of total iron was increased, as was hepatic ferritin and its saturation by iron. A striking increas e (approximately 7-fold) was also observed in free iron which appeared to be redox-active. The increase in liver free iron involved the hepa tocellular component of the liver. Since DNA is one of the cellular ta rgets of redox active iron, liver DNA from phenylhydrazine-treated rat s was analyzed by electrophoresis and found to be markedly fragmented. Experiments with isolated hepatocytes in culture or in suspension cha llenged with phenylhydrazine or Fe-nitrilotriacetate strongly suggeste d that the DNA damage was due to reactive iron rather than to the hepa tic metabolism of phenylhydrazine. The levels of 8-oxo-7,8 dihydro-2'- deoxyguanosine (8-oxodGuo), a specific marker of oxidative DNA damage, were significantly higher in phenylhydrazine-treated rats as compared to untreated controls. The prolongation of phenylhydrazine treatment over a period of 6 weeks resulted in a persistent damage to DNA and in phenotypic changes such as an increase in hepatocyte gamma-glutamyl t ranspeptidase (gamma-GT, EC 2.3.2.2) activity. Possible relationships between iron overload, iron release, DNA damage and tumor initiation a re discussed. (C) 1997 Elsevier Science Inc.