RELEASE OF XANTHINE OXIDASE (XO) TO THE SYSTEMIC CIRCULATION DURING RESUSCITATION AFTER SEVERE HYPOXEMIA

Abstract

XO may contribute to oxygen free radical production during reoxygenation after hypoxia, but in humans XO is present in substantial amounts only in liver and intestine and possibly to a smaller extent in vascular endothelium. We wanted to determine whether XO is released to the systemic circulation during reoxygenation after general hypoxia and thus possibly contributes to oxygen radical production in other organs also. Plasma levels of XO were determined in 19 newborn pigs resuscitated from severe hypoxemia (8% O2 until systolic blood pressure had fallen to 20 mmhg). 14C-xanthine was used as substrate, and the 14C-uric acid product was isolated with an HPLC technique and counted Plasma XO was below 2.5 μU/ml in all piglets before hypoxemia and in 4 control piglets throughout the experiment. In 5 of 19 piglets plasma XO rose during reoxygenation to a mean value of 10 {range 4 - 18) μU/ml after 30 min. In these piglets plasma aspartate aminotransferase increased also (from 20 to 94 U/l), but not alanine aminotransferase (36 to 39 U/ml). We conclude that XO may be released to the systemic circulation after severe hypoxia although in the present experiment XO was only elevated in 5 out of 19 piglets.