Mechanism of clearance and transfer of dipeptides by perfused human placenta.
Mechanism of clearance and transfer of dipeptides by perfused human placenta.
复制标题
灌注人胎盘清除和转移二肽的机制。
DOI：
10.1152/ajpendo.1996.271.3.e535
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Morse,E
中科院分区：
文献类型：
--
作者：
Adibi,SA;Schenker,S;Morse,E
甘氨酰谷氨酰胺（Gly-Gln）是肠外营养中稳定的谷氨酰胺来源。在本研究中，我们已经调查了这种二肽是否是完整的转移通过人胎盘。虽然胎盘灌注90分钟后，母体隔室中Gly-Gln（100 μ M）几乎完全消失，但胎儿隔室中仅出现少量这种二肽（< 6 μ M）。为了研究这种转移是否是由于跨细胞转运，用[3 H]Gly-Gln探测人胎盘的刷状缘膜囊泡，其显示没有摄取。为了研究水解是否是Gly-Gln消失的机制，用抗水解的甘氨酰肌氨酸（Gly-Sar）重复灌注研究。与Gly-Gln形成鲜明对比的是，灌注90分钟后，近80%的Gly-Sar保留在灌注液中（半衰期为24分钟对235分钟）。其余Gly-Sar在胎室中完整回收。在母体隔室中添加Gly-Gln增加了甘氨酸在母体和胎儿隔室中的蓄积，但未增加谷氨酰胺的蓄积。总之，我们的数据表明：1）灌注的人胎盘清除Gly-Gln的机制主要是水解，而Gly-Sar主要是被动扩散，2）胎盘对谷氨酰胺的偏好大于甘氨酸。
Glycylglutamine (Gly-Gln) is stable source of glutamine for parenteral nutrition. In the present study we have investigated whether this dipeptide is transferred intact across the human placenta. Although after 90 min of placental perfusion there was almost complete disappearance of Gly-Gln (100 microM) from the maternal compartment, only a small concentration of this dipeptide (< 6 microM) appeared in the fetal compartment. To investigate whether this transfer was due to transcellular transport, brush-border membrane vesicles of the human placenta were probed with [3H]Gly-Gln, which showed no uptake. To investigate whether hydrolysis was the mechanism of disappearance of Gly-Gln, the perfusion study was repeated with glycylsarcosine (Gly-Sar), which is resistant to hydrolysis. In sharp contrast to Gly-Gln, after 90 min of perfusion nearly 80% of Gly-Sar remained in the perfusate (half-life of 24 vs. 235 min). The rest of the Gly-Sar was recovered intact in the fetal compartment. The addition of Gly-Gln to the maternal compartment increased the accumulation of glycine, but not glutamine, in both the maternal and fetal compartments. In conclusion, our data suggest that 1) the mechanism of clearance of Gly-Gln by perfused human placenta is largely hydrolysis, whereas that of Gly-Sar is largely passive diffusion, and 2) the placenta has a greater preference for glutamine than for glycine.