Silver M, Fowden A L, Taylor P M, Knox J, Hill C M
Physiological Laboratory, Cambridge.
Exp Physiol. 1994 May;79(3):423-33. doi: 10.1113/expphysiol.1994.sp003777.
Blood amino acids were measured in twelve chronically catheterized mares and fetuses between 250 and 310 days gestation. The concentrations of the majority of individual amino acids were similar in maternal and fetal arterial blood and no gestational changes were detected. Only methionine, phosphoserine, 3-methyl-histidine and glutamine were consistently higher in the fetus than the mare, whilst certain other amino acids were higher in the maternal blood. Fasting the mares for 36 h led to significant falls in plasma glucose and rises in urea and maternal free fatty acids (FFA). Small but significant decreases in a few amino acids were seen in both fetus and mother, with an overall amino acid fall of 15% in the fetus and 13% in the mare. Virtually all amino acids had risen to basal values by 6 h after feeding. Intrafetal insulin (1 i.u./kg I.V.) as a bolus caused a more dramatic fall in fetal glucose than fasting, with no change in the mare. There were also rapid decreases in many amino acids by 30 min post-insulin and by 2 h all but five amino acids had fallen significantly. There was a drop in total fetal blood amino acids of 29%. These findings show that, in contrast to most other species studied, there is no overall feto-maternal gradient in blood amino acids in the mare, and that fasting leads to small falls in amino acid concentration, whereas intrafetal insulin induces a severe hypoglycaemia with dramatic decreases in almost all amino acids and no change in urea, suggesting a direct anabolic effect of insulin on fetal tissues.
对12匹长期插管的母马及其处于妊娠250至310天的胎儿进行了血液氨基酸测定。大多数单个氨基酸在母马和胎儿动脉血中的浓度相似，未检测到妊娠相关变化。只有蛋氨酸、磷酸丝氨酸、3-甲基组氨酸和谷氨酰胺在胎儿体内的浓度始终高于母马，而其他一些氨基酸在母马血液中的浓度更高。让母马禁食36小时导致血浆葡萄糖显著下降，尿素和母马游离脂肪酸（FFA）升高。胎儿和母马体内的几种氨基酸均出现小幅但显著的下降，胎儿体内氨基酸总体下降15%，母马体内下降13%。几乎所有氨基酸在喂食后6小时均回升至基础值。静脉推注胎儿胰岛素（1国际单位/千克）导致胎儿血糖下降幅度比禁食时更大，而母马血糖无变化。胰岛素注射后30分钟，许多氨基酸也迅速下降，到2小时时，除五种氨基酸外，其他所有氨基酸均显著下降。胎儿血液中总氨基酸下降了29%。这些发现表明，与大多数其他研究物种不同，母马血液氨基酸不存在整体的胎儿-母体梯度，禁食导致氨基酸浓度小幅下降，而胎儿体内注射胰岛素会引发严重低血糖，几乎所有氨基酸都大幅下降，尿素无变化，这表明胰岛素对胎儿组织有直接的合成代谢作用。
