Kravtsov G M, Pokudin N I, Orlov S N
Biokhimiia. 1979 Nov;44(11):2058-65.
Using the isotope exchange technique including 45Ca, the Ca2+-binding and Ca2+-accumulating capacity of mitochondria, sarcolemma and sarcoplasmic reticulum of rat heart was studied. The ATP-independent binding of Ca2+ to isolated membrane fractions is by 1--2 orders of magnitude less than the ATP-dependent Ca2+-accumulating capacity of the fractions. The Ca2+-accumulating capacity of mitochondria is increased 6--8 fold after addition of physiological concentrations of succinate and Pi to the incubation medium. Under these conditions the ratio of Ca2+-accumulating capacity of mitochondria, sarcolemma and sarcoplasmic reticulum of the heart is 100:3,12:2,9. The initial rate of Ca2+-uptake by the sarcoplasmic reticulum is much higher in comparison with sarcolemma and mitochondria. A high Ca2+-accumulating capacity of heart mitochondria probably determines a long-term regulation of the concentration of "troponin-accessible" Ca2+ in the sarcoplasm, whereas the high initial rate of Ca2+ accumulation by the sarcoplasmic reticulum provides for a rapid decrease of Ca2+ concentration during rhythmic contractions of the heart.
采用包括45Ca在内的同位素交换技术，研究了大鼠心脏线粒体、肌膜和肌浆网的Ca2+结合及Ca2+蓄积能力。Ca2+与分离的膜组分的非ATP依赖性结合比该组分的ATP依赖性Ca2+蓄积能力低1 - 2个数量级。向孵育介质中添加生理浓度的琥珀酸和无机磷酸盐后，线粒体的Ca2+蓄积能力增加6 - 8倍。在这些条件下，心脏线粒体、肌膜和肌浆网的Ca2+蓄积能力之比为100:3.12:2.9。与肌膜和线粒体相比，肌浆网摄取Ca2+的初始速率要高得多。心脏线粒体的高Ca2+蓄积能力可能决定了肌浆中“肌钙蛋白可及”Ca2+浓度的长期调节，而肌浆网Ca2+蓄积的高初始速率则使得心脏节律性收缩期间Ca2+浓度迅速下降。
