Becker G L, Fiskum G, Lehninger A L
J Biol Chem. 1980 Oct 10;255(19):9009-12.
Electrode measurements were made of the free Ca2+ concentration maintained by suspensions of isolated rat liver mitochondria and microsomes, as well as by hepatocytes whose plasma membranes had been made permeable by treatment with digitonin. When the KCl, ATP, Mg2+, and phosphate concentrations were made similar to that of cytosol, the steady state free Ca2+ concentration in the presence of respiring mitochondria alone was about 0.5 microM. The additional presence of rat liver microsomes resulted in a steady state level of close to 0.2 microM, which was maintaied for greater than 1 h at 25 degrees C. This concentration of Ca2+ was also maintained by suspensions of hepatocytes permeabilized by digitonin and thus may approximate the actual cytosolic free Ca2+ concentration in vivo. The "set point" for free Ca2+ homeostasis in these systems is determined by mitochondrial Ca2+ influx-efflux cycling, which is dependent on the level of intramitochondrial Ca2+ and can be adjusted by sequestration of Ca2+ in microsomes.
用电极测量了由分离的大鼠肝线粒体和微粒体悬浮液以及经洋地黄皂苷处理使其质膜具有通透性的肝细胞所维持的游离Ca2+浓度。当KCl、ATP、Mg2+和磷酸盐浓度与细胞质相似时，仅存在呼吸线粒体时的稳态游离Ca2+浓度约为0.5微摩尔。大鼠肝微粒体的额外存在导致稳态水平接近0.2微摩尔，在25℃下维持超过1小时。这种Ca2+浓度也由经洋地黄皂苷通透处理的肝细胞悬浮液维持，因此可能接近体内实际的细胞质游离Ca2+浓度。这些系统中游离Ca2+稳态的“设定点”由线粒体Ca2+流入-流出循环决定，该循环依赖于线粒体内Ca2+水平，并且可以通过微粒体中Ca2+的螯合来调节。
