Kuruvilla A G, D'Souza S W, Glazier J D, Mahendran D, Maresh M J, Sibley C P
Department of Child Health, University of Manchester, St. Mary's Hospital, United Kingdom.
J Clin Invest. 1994 Aug;94(2):689-95. doi: 10.1172/JCI117386.
Fetal macrosomia (FM) is a well-recognized complication of diabetic pregnancy but it is not known whether placental transport mechanisms are altered. We therefore studied the activity of the system A amino acid transporter, the system L amino acid transporter, and the Na+/H+ exchanger in microvillous membrane vesicles from placentas of macrosomic babies born to diabetic women (FM group), from placentas of appropriately grown babies born to diabetic women (appropriate for gestational age group) and from placentas of appropriately grown babies of normal women (control group). Sodium-dependent uptake of [14C]-methylaminoisobutyric acid at 30 s (initial rate, a measure of system A activity) was 49% lower into FM vesicles than into control vesicles (P < 0.02); this effect was due to a decrease in Vmax of the transporter with no change in Km. There was no significant difference in system A activity between the appropriate for gestational age group and control or FM group. There was also no difference between system L transporter or Na+/H+ exchanger activity between the three groups. We conclude that the number of system A transporters per milligram of membrane protein in the placental microvillous membrane is selectively reduced in diabetic pregnancies associated with FM.
巨大胎儿（FM）是糖尿病妊娠中一种公认的并发症，但尚不清楚胎盘转运机制是否发生改变。因此，我们研究了糖尿病女性所生巨大儿胎盘（FM组）、糖尿病女性所生发育正常胎儿胎盘（适于胎龄组）以及正常女性所生发育正常胎儿胎盘（对照组）微绒毛膜囊泡中A系统氨基酸转运体、L系统氨基酸转运体和Na⁺/H⁺交换体的活性。30秒时[¹⁴C] - 甲基氨基异丁酸的钠依赖性摄取（初始速率，衡量A系统活性）在FM囊泡中比对照组囊泡低49%（P < 0.02）；这种效应是由于转运体的Vmax降低而Km无变化所致。适于胎龄组与对照组或FM组之间的A系统活性无显著差异。三组之间的L系统转运体或Na⁺/H⁺交换体活性也无差异。我们得出结论，在与FM相关的糖尿病妊娠中，胎盘微绒毛膜中每毫克膜蛋白的A系统转运体数量选择性减少。
