Morin F C, Egan E A, Ferguson W, Lundgren C E
Department of Pediatrics, University at Buffalo, New York.
Am J Physiol. 1988 Mar;254(3 Pt 2):H542-6. doi: 10.1152/ajpheart.1988.254.3.H542.
The ability of the pulmonary circulation of the fetal lamb to respond to a rise in oxygen tension was studied from 94 to 146 days of gestation. The unanesthetized ewe breathed room air at normal atmospheric pressure, followed by 100% oxygen at three atmospheres absolute pressure in a hyperbaric chamber. In eleven near-term lambs (132 to 146 days of gestation), fetal arterial oxygen tension (PaO2) increased from 25 +/- 1 to 55 +/- 6 Torr (mean +/- SE), which increased the proportion of right ventricular output distributed to the fetal lungs from 8 +/- 1 to 59 +/- 5%. In five very immature lambs (94 to 101 days of gestation), fetal PaO2 increased from 27 +/- 1 to 174 +/- 70 Torr, but the proportion of right ventricular output distributed to the lung did not change, 8 +/- 1 to 9 +/- 1%. In five of the near-term lambs, pulmonary blood flow was measured. It increased from 34 +/- 3 to 298 +/- 35 ml.kg fetal wt-1.min-1, an 8.8-fold increase. We conclude that the pulmonary circulation of the fetal lamb does not respond to an increase in oxygen tension before 101 days of gestation; however, near term an increase in oxygen tension alone can induce the entire increase in pulmonary blood flow that normally occurs after the onset of breathing at birth.
在妊娠94至146天期间，研究了胎羊肺循环对氧分压升高的反应能力。未麻醉的母羊在正常大气压下呼吸室内空气，然后在高压舱内呼吸三个绝对大气压的100%氧气。在11只近足月羔羊（妊娠132至146天）中，胎儿动脉氧分压（PaO2）从25±1 Torr增加到55±6 Torr（平均值±标准误），这使得分配到胎儿肺部的右心室输出比例从8±1%增加到59±5%。在5只非常不成熟的羔羊（妊娠94至101天）中，胎儿PaO2从27±1 Torr增加到174±70 Torr，但分配到肺部的右心室输出比例没有变化，从8±1%到9±1%。在5只近足月羔羊中测量了肺血流量。它从34±3增加到298±35 ml·kg胎儿体重-1·min-1，增加了8.8倍。我们得出结论，妊娠101天前胎羊的肺循环对氧分压升高没有反应；然而，在接近足月时，仅氧分压升高就能诱发出生后呼吸开始后正常发生的肺血流量的全部增加。
