Treinen K A, Kulkarni A P
Department of Anatomy and Cell Biology, University of Michigan, Ann Arbor 48109.
Placenta. 1987 Sep-Oct;8(5):477-86. doi: 10.1016/0143-4004(87)90076-2.
In this communication, an ATP-dependent Ca2+ uptake was characterized in term human placental brush border membranes. Multiple freeze-thaw cycles greatly diminished uptake activity by 90 per cent, indicating an intravesicular accumulation of Ca2+. Kinetic studies indicate an apparent Km for Ca2+ of 0.22 +/- 0.04 microM and a Vmax of 441 +/- 137 pmoles/min/mg protein at 37 degrees C. The uptake was shown to have an optimum pH between 7.0 and 7.2, and was unaffected by the addition of oxalate, characteristics which are consistent with a plasma membrane origin of uptake. The process was temperature-dependent with a Q10 of 1.11 and was significantly inhibited (50 per cent) by 100 microM concentrations of trifluoperazine and vanadate. The characteristics of placental brush border Ca2+ uptake are similar to those of other Ca2+ uptake systems known to regulate intracellular calcium concentrations. By analogy, we suggest a similar role for this process in the maintenance of the low intracellular Ca2+ levels necessary for placental syncytiotrophoblast viability.
在本交流中，对足月人胎盘刷状缘膜中的一种ATP依赖性Ca2+摄取进行了表征。多次冻融循环使摄取活性大幅降低90%，表明Ca2+在囊泡内蓄积。动力学研究表明，在37℃时，Ca2+的表观Km为0.22±0.04微摩尔，Vmax为441±137皮摩尔/分钟/毫克蛋白质。摄取显示在pH 7.0至7.2之间有最佳值，且不受草酸盐添加的影响，这些特性与摄取源自质膜一致。该过程依赖温度，Q10为1.11，并被100微摩尔浓度的三氟拉嗪和钒酸盐显著抑制（50%）。胎盘刷状缘Ca2+摄取的特性与已知调节细胞内钙浓度的其他Ca2+摄取系统相似。由此类推，我们认为该过程在维持胎盘合体滋养层细胞活力所需的低细胞内Ca2+水平方面具有类似作用。
