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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adaptation to hyperoxia has been attributed to increased activities of protective enzymes, but we suggest that an additional factor may be the lung's capacity to repair itself in hyperoxia. Such repair would require increased polyamines, but there are reports that two key enzymes of polyamine metabolism are suppressed by hyperoxia or oxidants. Because rats can adapt to hyperoxia but mice cannot, we compared their changes of polyamine metabolism and judged cell repair by using [3H]thymidine to estimate DNA synthesis. Both species developed increased ornithine decarboxylase activity and putrescine content, but the mouse did not develop increased S-adenosylmethionine decarboxylase activities or increases of spermidine and spermine as did the rat when exposed to 85% O2. Furthermore, we confirmed that the rat lung does respond to hyperoxia with increased DNA synthesis, but the mouse lung does not. The results suggest that in addition to increased activities of protective enzymes, increased repair processes in the rat lung may play a role in its capacity to adapt to hyperoxia. The incomplete response of polyamine metabolism in mice may contribute to their inability to adapt in hyperoxia.
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PMID:Polyamines, DNA synthesis, and tolerance to hyperoxia of mice and rats. 291 88

To determine if lung cell replication and repair might be different between younger (30-day-old) and older (60-day-old) rats, we studied polyamine and DNA biosynthesis in rats exposed to 1.0 atm oxygen for 24, 48, 56, or 72 h. By 24 h, no statistically significant changes were observed, but by 48 h, ornithine decarboxylase and putrescine increased; S-adenosylmethionine decarboxylase activity increased by 56 h in the younger rats but not in the older rats. By 72 h, spermidine, [3H]thymidine incorporation, and the labeling index of cells in the alveolar zone had increased only in the younger rats. During the first 56 h, hyperoxia inhibited DNA synthesis. We conclude that hyperoxia initially suppresses lung cell replication but subsequently, if the rat survives, there are increases in polyamine biosynthesis and cell replication that may be important for the development of oxygen tolerance.
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PMID:Hyperoxic lung injury and polyamine biosynthesis. Age-related differences. 402 59