Effect of dexamethasone on pulmonary surfactant metabolism in hyperoxia-treated rat lungs.
We have examined the effect of dexamethasone on the metabolism of pulmonary surfactant in normal and hyperoxia-treated rats. The relative abundance of the surfactant-specific apoprotein A (SP-A) mRNA in lung tissues and the contents of disaturated phosphatidylcholine (DSPC) and SP-A were measured in bronchoalveolar lavage fluids and in lung tissues in 4-wk-old rats exposed to room air or greater than 90% oxygen for 7 d with or without simultaneous treatment with dexamethasone (0.5 mg/kg body wt for 7 d). The relative abundance of the SP-A mRNA was marginally increased by hyperoxia (1.3-fold over controls). Dexamethasone increased the relative abundance of the SP-A mRNA to a level comparable to that with hyperoxia treatment (1.5-fold over controls). In lavage fluids, the contents of DSPC and SP-A were increased by 4- and 6-fold over controls by hyperoxia, respectively, but they were increased only by 2-fold by dexamethasone. In lung tissues, the contents of DSPC and SP-A were increased by 3- and 2-fold over controls by hyperoxia, respectively. These values in lung tissues in the air-exposed rats were not significantly increased by dexamethasone. In hyperoxia-treated rats, dexamethasone did not significantly affect the relative abundance of the SP-A mRNA level and the contents of DSPC and SP-A in lavage fluids and lung tissues. These results indicate that mechanisms other than increased synthesis of SP-A are involved in hyperoxia-induced SP-A accumulation and that dexamethasone does not affect the abnormal accumulation of pulmonary surfactant induced by hyperoxia.
Ohashi
T
T
Department of Pediatrics, Kobe University School of Medicine, Japan.
Takada
S
S
Motoike
T
T
Tsuneishi
S
S
Matsuo
M
M
Sano
K
K
Nakamura
H
H
D000818:Animals; D001997:Bronchopulmonary Dysplasia / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control; D003907:Dexamethasone / Q000494:pharmacology*; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000235:genetics / Q000378:metabolism; D011510:Proteolipids / Q000235:genetics / Q000378:metabolism; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D010713:Phosphatidylcholines; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012333:RNA, Messenger; C017463:lecithins, disaturated; D003907:Dexamethasone; D010100:Oxygen