BACKGROUND: Induction of heme oxygenase (HOX) enzyme, the 32 kD stress protein as protection against heme toxicity and adaptation to oxidative stress has been proven in experimental conditions.

SUBJECTS: We studied the role of HOX activity in 40 arteficially ventillated premature infants (29.9±2 ws of gestation, 1502±358 g bw) with adaptational troubles. IRDS, intraventricular hemorrhage on the 1st, 3rd, and 5th days.

METHODS: Concentrations of plasma hemoglobin (Hb) metabolites (oximetHb, hemichrome) and bilirubin were estimated with spectrophotometry, and their ratio (Bi/Bi+Hb) was taken as an index of HOX activity.

RESULTS: In patients with good prognosis (n=30) both a higher initial activity index was shown, and there was also a considerable increase in it: 0.35 to 0.49 against the rise in fatal cases (n=10): 0.22 to 0.39 (median values: p<0.01). There were several prematures (n=10) whom later BPD and/or NEC/ROP developed. They had a decreased activity index (0.22) on the first day, and needed higher oxygen (100%) than the other recovered prematures(60%).

CONCLUSION: HOX activity has a definite role in the outcome of adaptation to extrauterine life in human prematures, and its activity can be assessed in plasma by its product/substrate ratio.