Gilbert W M, Newman P S, Eby-Wilkens E, Brace R A
Department of Obstetrics and Gynecology and Reproductive Medicine, University of California, Davis, USA.
Am J Obstet Gynecol. 1996 Dec;175(6):1557-62. doi: 10.1016/s0002-9378(96)70106-0.
This study examined the movement of the soluble ion technetium Tc 99m across the ovine placenta and intramembranous pathway.
Nineteen fetal sheep at 131 +/- 1 (SE) days' gestation were studied. After a 1-hour control period technetium Tc 99m was injected into either a fetal vein (n = 7), the amniotic cavity (n = 5), or a maternal vein (n = 5). Maternal and fetal blood, fetal urine, and amniotic and allantoic fluid were sampled during the control period and for 8 hours after the injection. Fetal urine was drained externally throughout the experiment. In five animals technetium Tc 99m was injected intraamniotically after the fetus was killed with air emboli and sampled as described.
Intrafetally injected technetium Tc 99m rapidly crossed the placenta; then it entered and was concentrated in the amniotic cavity. Intraamniotically injected technetium Tc 99m rapidly entered into the fetal circulation. The maternally injected technetium Tc 99m rapidly crossed the placenta into the fetus, suggesting a half-time for placental exchange of < 50 minutes. The technetium Tc 99m injected into the dead fetus group demonstrated significantly less maternal absorption than in the live fetus group.
The soluble ion technetium Tc 99m demonstrated a much more rapid movement in both directions across the ovine placenta then previously demonstrated for the smaller ion sodium. Technetium Tc 99m rapidly crossed the intramembranous pathway bidirectionally, suggesting a high permeability of the intramembranous pathway. Minimal maternal absorption of technetium Tc 99m in the dead fetus group suggests little transmembranous absorption by the mother.
本研究检测了可溶性离子锝Tc 99m在绵羊胎盘及膜内途径中的移动情况。
对19只妊娠131±1（标准误）天的胎羊进行研究。在1小时的对照期后，将锝Tc 99m注入胎儿静脉（n = 7）、羊膜腔（n = 5）或母体静脉（n = 5）。在对照期及注射后8小时采集母血和胎血、胎儿尿液、羊水和尿囊液样本。在整个实验过程中，胎儿尿液都被引流到体外。在5只动物中，在用空气栓塞杀死胎儿后，将锝Tc 99m注入羊膜腔内，并按上述方法进行采样。
经胎儿体内注射的锝Tc 99m迅速穿过胎盘；然后进入羊膜腔并在其中浓缩。经羊膜腔内注射的锝Tc 99m迅速进入胎儿循环。经母体注射的锝Tc 99m迅速穿过胎盘进入胎儿体内，提示胎盘交换的半衰期<50分钟。注入死胎组的锝Tc 99m的母体吸收明显少于活胎组。
可溶性离子锝Tc 99m在绵羊胎盘两侧的双向移动比之前所显示的较小离子钠要快得多。锝Tc 99m能迅速双向穿过膜内途径，提示膜内途径具有高通透性。死胎组中锝Tc 99m的母体吸收极少，表明母亲的跨膜吸收很少。
