RELEASE OF XANTHINE-OXIDASE TO THE SYSTEMIC CIRCULATION DURING RESUSCITATION FROM SEVERE HYPOXEMIA IN NEWBORN PIGS

Xanthine oxidase may contribute to oxygen free radical formation durin g reoxygenation after hypoxia, but in humans the enzyme is present in substantial amounts only in the liver and intestine. We developed a se nsitive assay for xanthine oxidase using C-14-xanthine as substrate an d investigated whether xanthine oxidase was released into the systemic circulation when 19 newborn pigs were resuscitated after severe hypox emia. In five piglets plasma xanthine oxidase concentrations increased from undetectable levels to a median value of 8 (range 4-18) mu U/ml after 30 min of reoxygenation. In these pigs serum aspartate aminotran sferase increased from 45 to 148 U/l, while alanine aminotransferase w as unchanged (28-31 U/l). The release of xanthine oxidase did not seem to correlate with the severity of the histological brain damage after 4 days. We conclude that only low levels of xanthine oxidase are rele ased to the systemic circulation after severe hypoxemia in newborn pig s.