Gurpide E, Marks C, de Ziegler D, Berk P D, Brandes J M
Am J Obstet Gynecol. 1982 Nov 1;144(5):551-5. doi: 10.1016/0002-9378(82)90226-5.
Human placentas were perfused in vitro through fetal vessels of a single cotyledon with a solution of tritiated androstenedione (A) or tritiated testosterone in oxygenated Krebs-Ringer bicarbonate buffer containing glucose. The same buffer, without labeled steroids, was used to perfuse the maternal side of the placenta. Fractions of unrecycled "fetal" and "maternal" perfusates were collected to estimate the steady-state rates of output into each perfusate of labeled estrone (E1) and estradiol (E2), formed by aromatization of the perfused androgens. An unequal distribution of the two estrogens was observed, i.e., a significantly larger proportion of E2 than of E1 was released to the maternal perfusate. Addition of unlabeled A or ethinyl estradiol (10(-5)M) to the fetal perfusion buffer resulted in a redistribution of the E2 output toward the fetal perfusate. These in vitro results are similar to the findings of Walsh and McCarthy, who detected by tracer experiments an unequality in the in vivo fetomaternal distribution of the output of placentally produced E1 and E2 in rhesus monkeys. These results also support the possibility of the existence of saturable specific E2 carriers in the syncytiotrophoblast, postulated by the same authors to explain their findings. However, an extrasyncytial conversion of E2 to E1 could also account for the disproportion in the relative output of the estrogens toward mother and fetus. The perfusion system used in these studies may be useful for the elucidation of factors determining the relative rates of placental secretion of steroids toward mother and fetus.
在含有葡萄糖的充氧克雷布斯-林格碳酸氢盐缓冲液中，将氚标记的雄烯二酮（A）或氚标记的睾酮溶液通过单个叶状绒毛膜的胎儿血管对人胎盘进行体外灌注。使用不含标记类固醇的相同缓冲液灌注胎盘的母体侧。收集未循环的“胎儿”和“母体”灌注液的馏分，以估计灌注雄激素经芳香化形成的标记雌酮（E1）和雌二醇（E2）进入每种灌注液的稳态输出率。观察到两种雌激素分布不均，即释放到母体灌注液中的E2比例明显大于E1。向胎儿灌注缓冲液中添加未标记的A或乙炔雌二醇（10^(-5)M）导致E2输出向胎儿灌注液重新分布。这些体外结果与Walsh和McCarthy的研究结果相似，他们通过示踪实验检测到恒河猴体内胎盘产生的E1和E2在母胎分布上的不平等。这些结果也支持了同一作者推测的合体滋养层中存在可饱和特异性E2载体的可能性，以解释他们的发现。然而，E2向E1的合体滋养层外转化也可以解释雌激素向母体和胎儿的相对输出比例不均衡的现象。这些研究中使用的灌注系统可能有助于阐明决定类固醇向母体和胎儿胎盘分泌相对速率的因素。
