Cerebral hypoxia-ischemia increases microsomal iron in newborn piglets

The primary cause of neurologic impairment in newborn infants is hypoxic-ischemic injury. Studies of the mechanisms involved in the damaging effects of hypoxia-ischemia and reperfusion in brain tissue indicate significant contributions from reactive oxygen species, with the loss of homeostatic control of intracellular iron an important determinant of oxidant-mediated damage. We investigated the effects of cerebral hypoxia-ischemia and reperfusion on the redistribution of nonheme iron in newborn piglets. Anesthetized newborn piglets were subjected to reductions in cerebral blood flow by phlebotomy and cervical cuff compression. Control animals were sham-operated. Subcellular fractions were isolated from brain tissue homogenates by differential centrifugation, and nonheme iron contents of these fractions were measured with ferene-S. Iron contents in the homogenates were not altered. However, iron contents of the microsomal fractions of animals subjected to 30 minutes of hypoxia-ischemia increased from 0.517 +/- 0.053 to 0.930 +/- 0.061 nmol/mg protein (p < 0.01); 120 minutes of reperfusion caused no further changes. This translocation of iron may be linked to oxidative alterations of brain proteins, which we investigated by detection of dinitrophenylhydrazine-derivitized protein carbonyls, which are characteristic of iron-catalyzed oxidation reactions.