Kinetic properties of the Ca2+-accumulation system of a rat liver microsomal fraction.
Kinetic properties of the Ca2+-accumulation system of a rat liver microsomal fraction.
复制标题
大鼠肝微粒体部分的 Ca2 累积系统的动力学特性。
作者：
A. Dawson
1. 通过使用Ca-EGTA缓冲液，发现Ca2+摄取到大鼠肝脏重微粒体（微粒体部分）的Km为0.2 microM游离Ca2+。2. 在缺乏草酸盐的情况下，这些囊泡每毫克蛋白质积累约20毫摩尔的Ca2+。Ca2+从囊泡流出的速度在pH 7.6比pH 6.8快得多，但没有明显表现出饱和动力学或对外部离子的任何严格要求。3. 在ATP存在和草酸缺乏的情况下，Ca2+在微粒体和培养基之间的稳态分布依赖于Ca2+负载。当囊泡负载至50%容量时，外部游离Ca2+浓度为70 nM。4. 重微粒体对Ca2+的亲和力是这样的，似乎它们在细胞质游离Ca2+浓度的测定中起主导作用。
1. By using Ca-EGTA buffers, the Km for Ca2+ uptake into rat liver heavy microsomes (microsomal fraction) was found to be 0.2 microM free Ca2+. 2. In the absence of oxalate, these vesicles accumulate about 20 nmol of Ca2+/mg of protein. Efflux of Ca2+ from the vesicles is much faster at pH 7.6 than at pH 6.8, but does not apparently show saturation kinetics or any stringent requirement for external ions. 3. The steady-state distribution of Ca2+ between the microsomes and the medium in the presence of ATP and the absence of oxalate is dependent on Ca2+ load. When the vesicles are loaded to 50% capacity, the external free Ca2+ concentration is 70 nM. 4. The affinity of heavy microsomes for Ca2+ is such that is seems likely that they has a dominant role in the determination of cytoplasmic free Ca2+ concentrations.