McGowan J E, Aldoretta P W, Hay W W
Division of Perinatal Medicine, University of Colorado School of Medicine, Denver 80262, USA.
Am J Physiol. 1995 Nov;269(5 Pt 1):E834-9. doi: 10.1152/ajpendo.1995.269.5.E834.
We examined the rate of production of [14C]fructose and [14C]lactate from [U-14C]glucose by the placenta and the contribution of 14CO2 from fetal oxidation of these metabolic products to the calculation of glucose oxidation rate in fetal sheep. During fetal tracer infusions (n = 16), oxidation of fructose contributed 16 +/- 3% of total fetal CO2 production; oxidation of lactate accounted for 3.3 +/- 0.1%. Thus 80% of total fetal CO2 production resulted from direct oxidation of carbon atoms in glucose; the "direct" glucose oxidation fraction was 0.46 +/- 0.04. During maternal tracer infusion (n = 15), CO2 production from fructose was 21 +/- 3, 20 +/- 3, and 30 +/- 4% and from lactate was 16 +/- 3, 13 +/- 3, and 11 +/- 4% in hypo-, normo-, and hyperglycemic animals, respectively; the direct glucose oxidation fraction was 0.40 +/- 0.04, not different from the fraction obtained with the fetal tracer infusion. Fetal oxidation of substrates derived from glucose metabolism in the placenta contributes significantly to fetal CO2 production. Fetal oxidation of placental products of a metabolic substrate tracer should be considered in studies of fetal oxidative metabolism.
我们研究了胎盘利用[U-¹⁴C]葡萄糖生成[¹⁴C]果糖和[¹⁴C]乳酸的速率，以及这些代谢产物在胎儿体内氧化产生的¹⁴CO₂对计算胎儿绵羊葡萄糖氧化速率的贡献。在胎儿输注示踪剂期间（n = 16），果糖氧化占胎儿总CO₂产生量的16±3%；乳酸氧化占3.3±0.1%。因此，胎儿总CO₂产生量的80%来自葡萄糖中碳原子的直接氧化；“直接”葡萄糖氧化比例为0.46±0.04。在母体输注示踪剂期间（n = 15），低血糖、正常血糖和高血糖动物中，果糖产生的CO₂分别为21±3%、20±3%和30±4%，乳酸产生的CO₂分别为16±3%、13±3%和11±4%；直接葡萄糖氧化比例为0.40±0.04，与胎儿输注示踪剂时得到的比例无差异。胎盘内源自葡萄糖代谢的底物在胎儿体内的氧化对胎儿CO₂产生有显著贡献。在胎儿氧化代谢研究中应考虑代谢底物示踪剂的胎盘产物在胎儿体内的氧化情况。
