Stacey T E, Weedon A P, Haworth C, Ward R H, Boyd R D
Am J Physiol. 1978 Jan;234(1):E32-7. doi: 10.1152/ajpendo.1978.234.1.E32.
The steady-state permeability of the placenta to radiolabeled 3-O-methyl--D-glucopyranose (3MeG), alpha-methyl-D-glucopyranoside (AMG), and D-xylose was measured in chronically catheterized conscious sheep near term. Fetomaternal flux was calculated by application of Fick's principle to the uterine circulation after injection to the fetus. At a fetal glucose concentration of 10.2 +/- 1.25 mM, the permeability of 3MeG was half the maximal value of 59.5 +/- 11.2 ml/min found by extrapolation to zero glucose concentration. The permeability to 3MeG is considerably greater than is compatible with restricted diffusion, which together with the competitive effect of D-glucose suggests a carrier-mediated transfer mechanism. The permeability to AMG was less than 0.1 ml/min. The specificity pattern of sugar transport from the fetal side of the sheep placenta is different from that reported for gut lumen or kidney tubule in other species. D-Xylose is not metabolically inert after its injection into the fetal lamb.
在接近足月的慢性插管清醒绵羊中，测量了胎盘对放射性标记的3-O-甲基-α-D-吡喃葡萄糖（3MeG）、α-甲基-D-吡喃葡萄糖苷（AMG）和D-木糖的稳态通透性。在向胎儿注射后，通过将菲克原理应用于子宫循环来计算母胎通量。在胎儿葡萄糖浓度为10.2±1.25 mM时，3MeG的通透性是通过外推至零葡萄糖浓度所发现的最大值59.5±11.2 ml/min的一半。3MeG的通透性远大于与受限扩散相符的值，这与D-葡萄糖的竞争效应一起表明存在载体介导的转运机制。AMG的通透性小于0.1 ml/min。绵羊胎盘胎儿侧糖转运的特异性模式与其他物种报道的肠腔或肾小管的模式不同。D-木糖注入胎羊后并非代谢惰性。
