Effects of the intraluminal Ca load on the kinetics of 45Ca uptake and efflux in brain microsomes.
Effects of the intraluminal Ca load on the kinetics of 45Ca uptake and efflux in brain microsomes.
复制标题
腔内 Ca 负荷对脑微粒体 45Ca 摄取和流出动力学的影响。
DOI：
10.1152/ajpcell.1996.271.5.c1472
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Abercrombie,RF
中科院分区：
文献类型：
--
作者：
Wells,KM;Abercrombie,RF
本文报道了增加脑内Ca（[Ca]i）对大鼠脑微粒体摄取和外排动力学的影响。分离的大鼠脑微粒体以囊外游离Ca（[Ca]o）和ATP依赖的方式积累45Ca。微粒体Ca负荷增加导致45 Ca摄取的初始速率降低，tau蛋白达到稳态蓄积63%的时间增加。离体大鼠脑微粒体以温度和[Ca] i依赖性方式丢失45 Ca。无论是否预先装载示踪剂45Ca和<或= 0.5或25 μ M [Ca]o，与37 ℃相比，4 ℃下的流出时间常数更大。此外，微粒体Ca负荷增加导致45Ca流出的时间常数降低。这种较短的流出时间常数不能解释在摄取期间[Ca]i对tau的影响，事实上，对于预载微粒体，[Ca]i对tau的影响更长。相反，这些数据表明，随着Ca积聚到未加载的微粒体中，稳定增加的[Ca]i减慢单向Ca流入（可能是通过抑制内质网Ca泵）并增强单向Ca流出，并且这些组合效应最终缩短了达到稳态管腔[Ca]i所需的时间。
Effects of increasing intraluminal Ca ([Ca]i) on the kinetics of rat brain microsomal uptake and efflux are reported here. Isolated rat brain microsomes accumulated 45Ca in an extravesicular free Ca ([Ca]o)- and ATP-dependent manner. Increased microsomal Ca load resulted in a decreased initial rate of 45Ca uptake and an increased tau, time to reach 63% of steady-state accumulation. Isolated rate brain microsomes lost 45Ca in a temperature- and [Ca]i-dependent manner. Whether preloaded with tracer 45Ca and either < or = 0.5 or 25 microM [Ca]o, the time constant of efflux was larger at 4 degrees C as compared with 37 degrees C. Additionally, increased microsomal Ca load resulted in a decreased time constant of 45Ca efflux. This shorter efflux time constant cannot explain the effect of [Ca]i on tau during uptake which was in fact longer for preloaded microsomes. Rather, these data suggest that, as Ca accumulates into unloaded microsomes, a steadily increasing [Ca]i slows unidirectional Ca influx (presumably by inhibiting the endoplasmic reticulum Ca pump) and enhances unidirectional Ca efflux, and that these combined effects ultimately shorten the time needed to achieve steady-state luminal [Ca]i.