Moll W, Kastendieck E
Respir Physiol. 1977 May;29(3):283-302. doi: 10.1016/0034-5687(77)90004-4.
The fetal vascular system of the guinea-pig placenta at term was perfused with a dextran solution at a rate of 3.6 and 9 ml/min, while the uteroplacental (maternal) blood flow was adjusted to 4-18 ml/min. N2O, CO, and tritiated water (HTO) were added to the perfusion fluid. The effectiveness of placental transfer of these substances, i.e. the actual transfer related to the maximum transfer occuring when the fetal vein equlibrates with the maternal artery, was calculated. It was found that the effectiveness of the CO transfer was 98% (SD = 2%). The effectiveness of the N2O transfer was about 90% (SD = 6%) when the maternofetal flow ratio was two and about 75% (SD = 13%) when the ratio was one. The effectiveness of the transfer was the same for HTO and N2O. It was concluded: (1) The vascular and diffusional shunts on the fetal side of the placenta are only 2%. (2) The placenta has the properties of a countercurrent system in which the effectiveness of gas transfer is decreased by about 25% at a flow ratio of one and by 10% at a flow ratio of two by inhomogeneity of the maternofetal flow ratio. (3) The diffusional resistance for HTO is unmeasurabbly small; its transfer is solely limited by blood flow.
给足月豚鼠胎盘的胎儿血管系统以3.6和9毫升/分钟的速率灌注葡聚糖溶液，同时将子宫胎盘（母体）血流调整至4 - 18毫升/分钟。向灌注液中添加一氧化二氮、一氧化碳和氚水（HTO）。计算这些物质胎盘转运的有效性，即与胎儿静脉与母体动脉达到平衡时发生的最大转运相关的实际转运。结果发现，一氧化碳转运的有效性为98%（标准差 = 2%）。当母胎血流比为2时，一氧化二氮转运的有效性约为90%（标准差 = 6%），当该比例为1时约为75%（标准差 = 13%）。HTO和一氧化二氮的转运有效性相同。得出以下结论：（1）胎盘胎儿侧的血管和扩散分流仅为2%。（2）胎盘具有逆流系统的特性，其中由于母胎血流比不均匀，在血流比为1时气体转运的有效性降低约25%，在血流比为2时降低10%。（3）HTO的扩散阻力小到无法测量；其转运仅受血流限制。
