Simmons R A, Charlton V E
Department of Pediatrics, CVRI, University of California, San Francisco 94143.
Pediatr Res. 1988 Jun;23(6):606-11. doi: 10.1203/00006450-198806000-00016.
In vivo substrate utilization has not been described for the maturing fetal lung. We, therefore, studied pulmonary delivery and use of major fetal substrates in six chronically catheterized fetal lambs over 119-141 days gestation. Oxygen, glucose, lactate, and alpha-amino nitrogen concentrations were measured in the pulmonary artery and pulmonary vein whereas lung blood flow was determined using labeled microspheres. We found that lung oxygen availability and use increased near term. Oxygen delivery averaged 4960 +/- 480 (SEM) microliters/min and rose with fetal age (p less than 0.05); uptake averaged 708 +/- 111 microliters/min and increased 93% near term (p less than 0.05). In contrast, glucose availability and use fell with gestation. Pulmonary artery glucose decreased with time (p less than 0.001), with a mean drop of 5.05 +/- 1.71 mg/dl in individual animals (p less than 0.05). Average glucose uptake was 844 +/- 225 micrograms/min and fell near term (p less than 0.05). Lactate was produced by the lung at a mean rate of 534 +/- 176 micrograms/min; this did not change with gestation. Lung amino nitrogen availability increased with fetal age. Pulmonary artery amino nitrogen rose by 1.35 mg/dl, or 43% (p less than 0.001) and lung delivery of amino nitrogen increased (p less than 0.05). The mean pulmonary glucose/O2 ratio was 1.48 +/- 0.26 and decreased with gestation (p less than 0.05), being less than 1.0 near term. The glucose-lactate/O2 ratio was 0.67 +/- 0.26, implying that 30% of lung oxidative metabolism is still unaccounted for. The alterations in delivery of substrates to the lung which were identified may serve as signals for pulmonary maturation, inducing the changes in lung metabolism that were found near term.
尚未有关于成熟胎儿肺脏体内底物利用情况的描述。因此，我们研究了119 - 141天妊娠期的6只长期插管的胎儿羔羊肺脏对主要胎儿底物的摄取和利用情况。测量了肺动脉和肺静脉中的氧气、葡萄糖、乳酸和α - 氨基氮浓度，同时使用标记微球测定肺血流量。我们发现，临近足月时肺脏的氧气供应和利用增加。氧气输送平均为4960±480（标准误）微升/分钟，并随胎龄增加而上升（p＜0.05）；摄取平均为708±111微升/分钟，临近足月时增加了93%（p＜0.05）。相比之下，葡萄糖的供应和利用随妊娠期增加而下降。肺动脉葡萄糖随时间降低（p＜0.001），个体动物平均下降5.05±1.71毫克/分升（p＜0.05）。葡萄糖摄取平均为844±225微克/分钟，临近足月时下降（p＜0.05）。肺脏产生乳酸的平均速率为534±176微克/分钟；这在妊娠期没有变化。肺脏氨基氮供应随胎龄增加。肺动脉氨基氮上升1.35毫克/分升，即43%（p＜0.001），肺脏氨基氮输送增加（p＜0.05）。平均肺脏葡萄糖/氧气比值为1.48±0.26，并随妊娠期降低（p＜0.05），临近足月时小于1.0。葡萄糖 - 乳酸/氧气比值为0.67±0.26，这意味着仍有30%的肺脏氧化代谢无法解释。所确定的底物向肺脏输送的变化可能作为肺成熟的信号，引发临近足月时所发现的肺代谢变化。
