PLASMA HYPOXANTHINE REACTS MORE ABRUPTLY TO CHANGES IN OXYGENATION THAN BASE DEFICIT AND URIC-ACID IN NEWBORN PIGLETS

Previously, high postmortem concentrations of hypoxanthine have been f ound in vitreous humor of children dying from sudden infant death synd rome (SIDS). We wanted to investigate further the accumulation of hypo xanthine in vitreous humor during hypoxia Twenty-four piglets aged 9-1 5 days were exposed to continuous hypoxemia (180 min 11% O-2, n = 6), long interval intermittent hypoxemia (60 min 11% O-2, 20 min room air, n = 7) or short interval intermittent hypoxemia (10 min 9% O-2, 10 mi n room air with (n = 6) or without (n = 5) superimposed ligation of bo th carotid arteries). The increase in vitreous humor Hyp was four-fold higher (p < 0.01) with ligation of the carotid arteries (14 +/- 2.4 t o 38 +/- 8.9 mu mol/l) than without ligation (15 +/- 2.8 to 21 +/- 5.9 mu mol/l). During continuous hypoxemia, plasma Hyp (r = 0.85), Xa (r = 0.89) uric acid (UA) (r = 0.85), and base deficit (ED) (r = 0.78) in creased almost linearly (p < 0.001). Plasma Hyp responded more abruptl y to changes in oxygenation than base deficit (BD) and UA. Ligation of the carotid arteries had a strong impact on Hyp accumulation in vitre ous humor, suggsting that vitreous humor Hyp is not merely a filtratio n product of plasma Hyp, but reflects local hypoxia/ischemia in the ey e.