Heme oxygenase-1 expression in premature and mature neonates during the first week of life.

Newborns are exposed to mechanical and oxidative stress during labor and to relative hyperoxia thereafter during the course of adaptation to the extrauterine conditions. Part of the adaptation mechanism is the rapid degradation of fetal hemoglobin and the oxidation of its heme moiety by heme oxygenases (HOs). Heme oxygenase-1 enzyme (HO-1) is the inducible isoform, which is induced by and protective against oxidative stress. We hypothesized that HO-1 may play a role in the physiological adaptation of newborns. We therefore measured the HO-1 mRNA expression with cRT-PCR during the first week after birth in healthy mature and premature newborns. We found that HO-1 was induced until day 2 or 3 after birth, but its level had dropped below the birth HO-1 mRNA level by the end of the first week. HO-1 levels and inducibility were similar in mature newborns and premature newborns. The fact that HO-1 was inducible even in gestation week 26 suggests that HO-1 plays an important role in the early adaptation processes.