Crandell S S, Palma P A, Morriss F H
Am J Obstet Gynecol. 1982 Jan 15;142(2):219-24. doi: 10.1016/s0002-9378(16)32340-7.
In 18 chronically instrumented pregnant ewes in late gestation, umbilical extractions of glucose and lactate were determined before and during the continuous infusion of ovine insulin, 0.25 mU/kg . min, into one uterine artery. Studies were conducted in both well-nourished and fasting ewes. Exogenous insulin increased the umbilical extraction of glucose without altering the umbilical extraction of lactate over the range of concentrations of maternal blood glucose encountered in the fed and fasted states. Moreover, the efflux of lactate into the uterine venous circulation in two additional ewes was not altered by the administration of insulin. These studies support the hypothesis that maternal circulating insulin binds to insulin receptors on the microvillous brush border of the placenta to effect an increase in the carrier-mediated transfer of glucose rather than cause an intraplacental decrease in the catabolism of glucose to lactate. The results suggest that, as maternal levels of blood glucose and serum insulin spontaneously rise in concert over the physiologic range, both factors may contribute to the increasing umbilical extraction of glucose. Furthermore, these observations raise the possibility that decreased binding of insulin by placental insulin receptors, which is reported to occur in placentas from diabetic women, may be accompanied by a relatively decreased umbilical uptake of glucose for a given maternal concentration of glucose, but not of lactate.
在18只处于妊娠晚期且长期植入监测装置的怀孕母羊中，在向一条子宫动脉持续输注0.25 mU/kg·min的绵羊胰岛素之前和期间，测定脐部对葡萄糖和乳酸的摄取量。研究在营养良好和禁食的母羊中均进行。在进食和禁食状态下所遇到的母体血糖浓度范围内，外源性胰岛素增加了脐部对葡萄糖的摄取，而未改变脐部对乳酸的摄取。此外，在另外两只母羊中，胰岛素的给药并未改变乳酸向子宫静脉循环的外流。这些研究支持以下假说：母体循环中的胰岛素与胎盘微绒毛刷状缘上的胰岛素受体结合，从而使载体介导的葡萄糖转运增加，而非导致胎盘内葡萄糖分解为乳酸的过程减少。结果表明，随着母体血糖水平和血清胰岛素水平在生理范围内自发协同升高，这两个因素可能都有助于脐部对葡萄糖摄取的增加。此外，这些观察结果提出了一种可能性，即在糖尿病女性的胎盘里，据报道胎盘胰岛素受体与胰岛素的结合减少，在母体葡萄糖浓度给定的情况下，可能伴随着脐部对葡萄糖的摄取相对减少，但对乳酸的摄取则不然。
