Fetal lung growth: influence of maternal hypoxia and hyperoxia in rats.
The consequences of maternal hypoxia and hyperoxia on maternal and fetal lung growth and in particular on the relationship between the three gas exchange organs (lungs and placenta) were studied in albino rats. Pregnant rats were exposed to one of the following: (1) 10% O2 in N2 or 100% O2 for 2 days beginning at day 7, 11, 14, or 18 of pregnancy; (2) 10% O2 in N2 or 100% O2 for 10 h/day beginning at day 7; or (3) 14-11% O2 in N2 continuously beginning at day 14 till day 21 when they were sacrificed. Maternal lung growth was assessed by measuring the lung weight, lung air volume and lung DNA content, and the fetal lung growth by lung DNA content. Hypoxia and hyperoxia of short duration (2 days) had no significant effect on maternal and fetal lungs and placenta. The major findings with intermittent hypoxia and hyperoxia, and with 1 week continuous hypoxia were as follows: (1) hypoxia initiated enlargement in maternal lung, liver, kidney and heart, and growth retardation in the fetus; (2) the direct relationships which exist in normal pregnancy between placental weight or DNA content and fetal body weight were abolished by maternal hypoxia, and that which exists between maternal and fetal lung DNA content, by hypoxia and hyperoxia; (3) both hypoxia and hyperoxia, applied at early pregnancy, caused small for body weight placenta and lung; and (4) neither maternal hypoxia nor hyperoxia influenced fetal lung maturation. It is speculated that reduction in fetal lung DNA content with maternal hypoxia may result from the direct and indirect effects of hypoxia on fetal lung, namely inhibition of cell multiplication and reduced pulmonary blood flow; and that a small fetal lung with maternal exposure to 100% O2, may result from redistribution of blood flow and nutrient supplies to fetal organs with lungs receiving a smaller proportion of it.
Department of Physiology, University of Manitoba, Winnipeg, Canada.
E E
EE
Faridy
M R
MR
Sanii
J A
JA
Thliveris
D000818:Animals; D004247:DNA / Q000378:metabolism; D005314:Embryonic and Fetal Development; D005260:Female; D005312:Fetal Blood; D005333:Fetus / Q000033:anatomy & histology; D000860:Hypoxia / Q000473:pathology / Q000503:physiopathology*; D008168:Lung / Q000196:embryology* / Q000473:pathology; D010100:Oxygen / Q000097:blood*; D010920:Placenta / Q000378:metabolism / Q000473:pathology; D011013:Pneumonectomy; D011247:Pregnancy; D011248:Pregnancy Complications; D051381:Rats
D004247:DNA; D010100:Oxygen