[Ca2+-accumulating capacity of mitochondria, sarcolemma and sarcoplasmic reticulum of rat heart].
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.
D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D007700:Kinetics; D008929:Mitochondria, Heart / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D012508:Sarcolemma / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
D002118:Calcium
Ca-akkumuliruiushchaia sposobnost' mitokhondriĭ sarkolemmy i saroplazmaticheskogo retikuluma serdtsa krysy.