Philipps A F, Dubin J W, Raye J R
Am J Obstet Gynecol. 1981 Jan;139(1):22-6. doi: 10.1016/0002-9378(81)90405-1.
Insulin secretion in the fetus may be important in the modulation of selected fetal amino acid concentration and uptakes. To test this hypothesis we observed the changes in fetal alanine concentrations and uptake after tolbutamide-induced insulin release in the fetal lamb. The basal umbilical venous-arterial alanine difference was 29.1 +/- 4.2 mumoles/L. Fetal alanine uptake was 5.1 +/- 0.6 mumoles/kg/min. After tolbutamide infusion fetal insulin concentration rose fourfold by 30 minutes. Fetal glucose concentration fell to approximately 75% of control values. Both arterial and umbilical venous alanine contents fell significantly (p < 0.01), yet the fetal alanine venous-arterial difference also fell significantly (p < 0.05) by 30 minutes. Fetal alanine uptake from the pooled experiments did not change significantly after tolbutamide. When only insulin responses of less than 150 microU/ml were considered, however, a significant (p < 0.02) fall in alanine uptake was noted. Two injections in one animal caused peak insulin levels above 150 microU/ml. Although limited, data from these latter experiments suggested an increase in fetal alanine uptake at these higher insulin concentrations. Thus, endogenous fetal insulin release caused a significant hyperinsulinism and consequent hypoglycemia. The fetal hypoalaninemia produced may have been due to a number of factors, including an acute decrease in placental alanine transfer and decreased fetal hepatic gluconeogenesis. A differential effect of high versus low insulin responses upon fetal alanine uptake is also suggested.
胎儿胰岛素分泌可能在调节特定胎儿氨基酸浓度和摄取方面具有重要作用。为了验证这一假设，我们观察了在胎羊中甲苯磺丁脲诱导胰岛素释放后胎儿丙氨酸浓度和摄取的变化。脐静脉 - 动脉丙氨酸基础差值为29.1±4.2微摩尔/升。胎儿丙氨酸摄取量为5.1±0.6微摩尔/千克/分钟。输注甲苯磺丁脲后30分钟，胎儿胰岛素浓度升高了四倍。胎儿葡萄糖浓度降至对照值的约75%。动脉和脐静脉丙氨酸含量均显著下降（p<0.01），然而，30分钟时胎儿丙氨酸静脉 - 动脉差值也显著下降（p<0.05）。在汇总实验中，甲苯磺丁脲处理后胎儿丙氨酸摄取量没有显著变化。然而，当仅考虑胰岛素反应小于150微单位/毫升时，丙氨酸摄取量显著下降（p<0.02）。在一只动物中进行两次注射导致胰岛素峰值水平高于150微单位/毫升。尽管这些后期实验的数据有限，但表明在这些较高胰岛素浓度下胎儿丙氨酸摄取增加。因此，内源性胎儿胰岛素释放导致显著的高胰岛素血症和随之而来的低血糖症。所产生的胎儿低丙氨酸血症可能是由于多种因素，包括胎盘丙氨酸转运的急性减少和胎儿肝脏糖异生的减少。还提示了高胰岛素反应与低胰岛素反应对胎儿丙氨酸摄取的不同影响。
