Comparative responses of premature versus full-term newborn rats to prolonged hyperoxia.
Because fetal rat lungs have lower baseline levels of both surfactant and antioxidant enzymes than full-term newborn rats, we questioned whether prematurely delivered rats might be more susceptible to O2 toxicity than those born at term. In the present studies, prematurely delivered rats (gestational d 21 of 22) and full-term rat pups were simultaneously put in > 95% O2 after birth. Surprisingly, we found that the preterm rats were not more susceptible to O2-induced lung damage and lethality than full-term newborns, but, in fact, the composite percentage of survival was even greater in the preterm pups from 7 to 9 d in hyperoxia and were similar thereafter up to 14 d in high O2. In addition, the preterm rats showed significantly decreased lung wet/dry weight ratios and consistently less severe pathologic evidence of pulmonary edema compared with term rats at 6 and 8 d of O2 exposure. The premature pups demonstrated the capability of inducing pulmonary antioxidant enzyme responses to hyperoxia by 3 d, and had significantly elevated copper-zinc superoxide dismutase, catalase, and glutathione peroxidase activities (and lung surfactant contents) at 6 d of O2 exposure compared with the term rats in O2. The rates of lung total O2 consumption and cyanide-resistant O2 consumption at d 6 in hyperoxia were not different for preterm versus term pups.(ABSTRACT TRUNCATED AT 250 WORDS)
Chen
Y
Y
Department of Medicine, University of Miami School of Medicine, Florida 33101.
Whitney
P L
PL
Frank
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L
D000818:Animals; D000831:Animals, Newborn; D000975:Antioxidants / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D005260:Female; D005865:Gestational Age; D005979:Glutathione Peroxidase / Q000378:metabolism; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D055370:Lung Injury; D008297:Male; D010100:Oxygen / Q000633:toxicity*; D010101:Oxygen Consumption; D010743:Phospholipids / Q000378:metabolism; D011247:Pregnancy; D011663:Pulmonary Surfactants / Q000378:metabolism; D051381:Rats; D013482:Superoxide Dismutase / Q000378:metabolism
D000975:Antioxidants; D010743:Phospholipids; D011663:Pulmonary Surfactants; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D010100:Oxygen