Philipps A F, Rosenkrantz T S, Lemons J A, Knox I, Porte P J, Raye J R
Department of Pediatrics, University of Connecticut Health Centre Farmington 06032.
J Dev Physiol. 1990 May;13(5):251-9.
To investigate the role of insulin in modulation of fetal amino acid metabolism, insulin infusions were performed in 10 chronically-catheterized fetal lambs. Fetal insulin infusion caused a dose related fall in the arterial blood concentrations of 13 of 15 amino acids studied as well as a 15-25% decrease in total amino acid concentration. Fetal lambs exhibited a biphasic response of umbilical total amino acid uptake when compared to fetal blood insulin concentration, i.e., at achieved fetal insulin concentrations less than 100 microU/ml, umbilical uptake of 9 specific amino acids as well as summed amino acid uptake from the umbilical circulation were depressed, but at insulin concentrations of 100-350 microU/ml, amino acid uptakes were similar to or above control values. Insulin infusion also caused a drastic diminution in the rate of fetal urea excretion. These findings suggest that insulin acts in the fetus to depress amino acid catabolism, thus altering amino acid extraction and uptake. Depressed protein catabolism with or without enhanced amino acid uptake would have the theoretical effect of stimulation of net protein synthesis with a shift toward use of nonprotein substrates for energy purposes.
为研究胰岛素在调节胎儿氨基酸代谢中的作用，对10只长期插管的胎儿羔羊进行了胰岛素输注。胎儿胰岛素输注导致所研究的15种氨基酸中的13种动脉血浓度呈剂量相关下降，总氨基酸浓度下降15 - 25%。与胎儿血胰岛素浓度相比，胎儿羔羊脐部总氨基酸摄取呈现双相反应，即当胎儿胰岛素浓度低于100微单位/毫升时，9种特定氨基酸的脐部摄取以及脐循环中总氨基酸摄取均降低，但在胰岛素浓度为100 - 350微单位/毫升时，氨基酸摄取与对照值相似或高于对照值。胰岛素输注还导致胎儿尿素排泄率大幅降低。这些发现表明，胰岛素在胎儿体内作用于抑制氨基酸分解代谢，从而改变氨基酸的提取和摄取。无论有无氨基酸摄取增加，蛋白质分解代谢降低在理论上都有刺激净蛋白质合成的作用，并促使转向利用非蛋白质底物作为能量来源。
