Carter B S, Moores R R, Battaglia F C, Meschia G
Department of Pediatrics, University of Colorado School of Medicine, Denver 80262.
Am J Physiol. 1993 Feb;264(2 Pt 1):E221-5. doi: 10.1152/ajpendo.1993.264.2.E221.
In a study of the metabolic implications of the large placental-to-fetal mass ratio that characterizes early fetal development, fetal plasma lactate disposal rate and CO2 production from fetal plasma lactate by fetus and placenta were measured in six midgestation (71-80 days) pregnant sheep. A constant fetal intravenous infusion of L-[U-14C]lactate and 3H2O was given to establish fetal steady-state lactate specific activity and to measure uterine and umbilical blood flows. Fetal and placental weights were 158.6 +/- 19.7 and 441.9 +/- 32.7 g, respectively. There was a significant net lactate flux into the uterine circulation (31 +/- 4.3 mumol/min, P < 0.01) but no measurable umbilical uptake. Fetal plasma lactate disposal rate was 21.2 +/- 2.7 mumol/min, approximately one-half of which represented fetal lactate flux into the placenta (9.9 +/- 1.9 mumol/min). The oxidation rate of tracer lactate carbon to 14CO2 by placenta plus fetus was 72.6 +/- 4.7% of the infused tracer and was fairly evenly distributed between the placenta and the fetus (42.4 +/- 3.9 vs. 30.3 +/- 2.2%). The midgestation placenta metabolizes and produces fetal plasma lactate at rapid and nearly equal rates. This contrasts with the late-gestation placenta, which makes a small contribution to fetal lactate disposal and is a major net source of fetal lactate.
在一项关于早期胎儿发育特征性的大胎盘与胎儿质量比的代谢影响研究中，对6只妊娠中期（71 - 80天）的怀孕绵羊测量了胎儿血浆乳酸清除率以及胎儿和胎盘从胎儿血浆乳酸中产生的二氧化碳量。通过持续静脉输注L - [U - ¹⁴C]乳酸和³H₂O来建立胎儿稳态乳酸比活度，并测量子宫和脐血流量。胎儿和胎盘重量分别为158.6±19.7克和441.9±32.7克。有显著的乳酸净通量进入子宫循环（31±4.3微摩尔/分钟，P < 0.01），但未检测到脐部摄取。胎儿血浆乳酸清除率为21.2±2.7微摩尔/分钟，其中约一半代表胎儿乳酸流入胎盘的通量（9.9±1.9微摩尔/分钟）。胎盘加胎儿将示踪乳酸碳氧化为¹⁴CO₂的速率为注入示踪剂的72.6±4.7%，且在胎盘和胎儿之间分布相当均匀（42.4±3.9%对30.3±2.2%）。妊娠中期的胎盘以快速且几乎相等的速率代谢并产生胎儿血浆乳酸。这与妊娠晚期的胎盘形成对比，妊娠晚期胎盘对胎儿乳酸清除的贡献较小，且是胎儿乳酸的主要净来源。
