Thomas C R, Lowy C
J Dev Physiol. 1983 Oct;5(5):323-32.
Using an in situ perfusion of the fetal side of the guinea-pig placenta the quantitative effects of changes in the perfusate flow rate and albumin concentration, and of changes in the transplacental free fatty acid (FFA) concentration gradient on FFA transfer across the placenta were investigated. Unidirectional transfer from mother to perfusate was assessed by the transfer of [14C]palmitic acid given as a constant infusion to the mother. The results of bidirectional FFA flux were assessed by measuring total unlabelled FFA accumulated by the perfusate during a single passage through the placenta. In 4 animals a factorial experiment was performed using perfusate in which the albumin concentration was changed from 1 to 3g/dl, whilst the flow was maintained at either 1 or 3 ml/min. A change from 1 to 3g/dl albumin averaged over both flow rates caused a significant increase in labelled palmitate, and unlabelled net FFA transfer, both for each ml of perfusuate (P less than 0.05, P less than 0.001) and for each minute of perfusion (P less than 0.005, P less than 0.001, respectively). A change from 1 to 3 ml/min flow rate averaged over both albumin concentrations caused a significant (P less than 0.001) decrease in labelled palmitate but no change in unlabelled FFA transfer per ml, but caused significant increases in labelled and unlabelled (P less than 0.05, P less than 0.001) FFA transfer per minute. From the results of these experiments and 32 more non-factorial experiments it was found that, whilst maternal and perfusate FFA concentrations were in the normal range, maternal plasma FFA levels significantly correlated (P less than 0.01) with net FFA transfer to the perfusate. When maternal plasma FFA levels became elevated then this relationship broke down. Inflowing perfusate FFA levels significantly (P less than 0.001) negatively correlated with net transfer, which changed direction and resulted in FFA transfer from perfusate to maternal blood when inflowing perfusate levels exceeded 1.7 microM/ml. It was concluded that the increases reported in fetal plasma albumin and flow rate as gestation advances enable the fetus to obtain increasing amounts of circulating maternal lipid. If this lipid is not extracted by the fetus then the reduction in the transplacental gradient will reduce net fat transfer to the fetus.
利用豚鼠胎盘胎儿侧的原位灌注，研究了灌注液流速和白蛋白浓度的变化，以及跨胎盘游离脂肪酸（FFA）浓度梯度的变化对FFA跨胎盘转运的定量影响。通过向母体持续输注[14C]棕榈酸来评估从母体到灌注液的单向转运。通过测量灌注液单次通过胎盘期间积累的总未标记FFA来评估双向FFA通量的结果。在4只动物中进行了一项析因实验，使用的灌注液中白蛋白浓度从1g/dl变为3g/dl，同时流速保持在1ml/min或3ml/min。在两种流速下，白蛋白浓度从1g/dl变为3g/dl的变化，导致每毫升灌注液中标记棕榈酸和未标记净FFA转运均显著增加（P<0.05，P<0.001），以及每分钟灌注时也显著增加（分别为P<0.005，P<0.001）。在两种白蛋白浓度下，流速从1ml/min变为3ml/min的变化，导致标记棕榈酸显著减少（P<0.001），但每毫升未标记FFA转运无变化，但每分钟标记和未标记FFA转运均显著增加（P<0.05，P<0.001）。从这些实验结果以及另外32个非析因实验中发现，当母体和灌注液FFA浓度在正常范围内时，母体血浆FFA水平与向灌注液的净FFA转运显著相关（P<0.01）。当母体血浆FFA水平升高时，这种关系就会破裂。流入灌注液中的FFA水平与净转运显著负相关（P<0.001），当流入灌注液水平超过1.7μM/ml时，净转运方向改变，导致FFA从灌注液转移到母体血液中。得出的结论是，随着妊娠进展，胎儿血浆白蛋白和流速增加，使胎儿能够获得越来越多的循环母体脂质。如果这种脂质未被胎儿摄取，那么跨胎盘梯度的降低将减少向胎儿的净脂肪转运。
