A comparative study of the calcium accumulation by mitochondria and microsomes isolated from the smooth muscle of the guinea-pig taenia coli
- 1 January 1977
- journal article
- research article
- Published by Springer Nature in Pflügers Archiv - European Journal of Physiology
- Vol. 368 (3), 217-223
- https://doi.org/10.1007/bf00585199
Abstract
The calcium uptake by mitochondria and microsomes isolated from the guinea-pig taenia coli was studied at physiological Ca2+ concentrations, buffered by Ca-EGTA mixtures. The Ca accumulation by the mitochondria was measured from the difference between the amount of Ca taken up in the presence and in the absence of a specific mitochondrial inhibitor. The Ca uptake by the microsomes was determined in a solution containing oxalate and a mitochondrial inhibitor. It was calculated from the difference in Ca uptake measured with and without ATP. By using this procedure, the necessity of extensive purification of the isolated fractions was avoided. The (Ca2+) for half-maximal transport in the mitochondria is 7×10−6 M. At (Ca2+) lower than 2×10−7 M, Ca is taken up in an energy-dependent way. In the microsomes the apparentKm for Ca is 7×10−7 M. Accumulation is still stimulated by ATP at a (Ca2+) as low as 4×10−8 M. The results show that the rate of Ca uptake by the cell organelles corresponding to the microsomal vesicles is sufficiently fast to explain the speed of relaxation of the taenia coli. The results also suggest that these cell organelles are more important than the mitochondria in regulating the cytoplasmic Ca concentration.Keywords
This publication has 25 references indexed in Scilit:
- Preparation and Properties of Vertebrate Smooth‐Muscle Myofibrils and ActomyosinEuropean Journal of Biochemistry, 1975
- Mitochondria, Ca2+ transport and the regulation of heart contraction and metabolismJournal of Molecular and Cellular Cardiology, 1975
- Calcium-Activated Tension of Skinned Muscle Fibers of the FrogThe Journal of general physiology, 1974
- ELECTRON MICROSCOPY AND ELECTRON PROBE ANALYSIS OF MITOCHONDRIAL CATION ACCUMULATION IN SMOOTH MUSCLEThe Journal of cell biology, 1974
- ANALYTICAL STUDY OF MICROSOMES AND ISOLATED SUBCELLULAR MEMBRANES FROM RAT LIVERThe Journal of cell biology, 1974
- Mechanisms for Intracellular Calcium Regulation in HeartThe Journal of general physiology, 1973
- The role of mitochondrial calcium uptake in contraction and relaxation of the human myometriumBiochimica et Biophysica Acta (BBA) - Bioenergetics, 1973
- Localization of Calcium Pump Activity in Smooth MuscleScience, 1973
- Role of Calcium Binding by Sarcoplasmic Reticulum in the Contraction and Relaxation of Uterine Smooth MuscleThe Journal of general physiology, 1969
- The dependence of contraction and relaxation of muscle fibres from the crab Maia squinado on the internal concentration of free calcium ionsBiochimica et Biophysica Acta (BBA) - Specialized Section on Biophysical Subjects, 1964