Sarcoplasmic reticulum. IX. The permeability of sarcoplasmic reticulum membranes.
P. F. Duggan,A. Martonosi +1 more
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Inulin penetration occurred at pH 7.0 with 1 mM EDTA and at pH 9.0 without EDTA, suggesting increased permeability of FSR membranes, which accords with the higher rate of Ca++ release from FSR at temperatures over 30°C, and the penetration of microsomal membranes by anions is markedly influenced by charge effects.Abstract:
Fragmented sarcoplasmic reticulum (FSR) membranes isolated from rabbit skeletal muscle are impermeable to inulin-14C (mol wt 5,000), and dextran-14C (mol wt 15,000–90,000) at pH 7.0–9.0, yielding an excluded space of 4–5 µl/mg microsomal protein. In the same pH range urea and sucrose readily penetrate the FSR membrane. EDTA or EGTA (1 mM) increased the permeability of microsomes to inulin-14C or dextran-14C at pH 8–9, parallel with the lowering of the FSR-bound Ca++ content from initial levels of 20 nmoles/mg protein to 1–3 nmoles/mg protein. EGTA was as effective as EDTA, although causing little change in the Mg++ content of FSR. The permeability increase caused by chelating agents results from the combined effects of high pH and cation depletion. As inulin began to penetrate the membrane there was an abrupt fall in the rate of Ca++ uptake and a simultaneous rise in ATPase activity. At 40°C inulin penetration occurred at pH 7.0 with 1 mM EDTA and at pH 9.0 without EDTA, suggesting increased permeability of FSR membranes. This accords with the higher rate of Ca++ release from FSR at temperatures over 30°C. The penetration of microsomal membranes by anions is markedly influenced by charge effects. At low ionic strength and alkaline pH acetate and Cl are partially excluded from microsomes when applied in concentrations not exceeding 1 mM, presumably due to the Donnan effect. Penetration of microsomal water space by acetate and Cl occurs at ionic strengths sufficiently high to minimize charge repulsions.read more
Citations
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Journal ArticleDOI
Calcium release from the sarcoplasmic reticulum
TL;DR: The inhibitors of Ca-induced Ca release––procaine and adenine––were shown not to inhibit contraction of living skeletal muscle fibers induced by the depolarization of the surface membrane.
Journal ArticleDOI
Effects of pH on the myofilaments and the sarcoplasmic reticulum of skinned cells from cardiace and skeletal muscles.
Fabiato A,F Fabiato +1 more
TL;DR: It was concluded that the effects of acidosis on the cardiac sarcoplasmic reticulum accentuate the depressive action of decreasing pH on the myofilaments, which may explain the pronounced depression of contractility observed during acidosis in cardiac muscle.
Journal ArticleDOI
Calcium release from the sarcoplasmic reticulum.
Fabiato A,F Fabiato +1 more
TL;DR: A review of the mechanism of Ca release from the SR of cardiac muscle and this is compared to release in skeletal muscle, and two processes have been proposed as possible links between the action potential of the sarcolemma and the release of Ca from theSR: the Ca-induced release ofCa and the "depolarization-induced"release of Ca.
Journal ArticleDOI
Isolation of sarcoplasmic reticulum by zonal centrifugation and purification of Ca2+-pump and Ca2+-binding proteins
TL;DR: The procedure for the isolation of highly purified sarcoplasmic reticulum vesicles from rabbit skeletal muscle has been described using sucrose gradient centrifugation in zonal rotors and enrichment in the level of phosphoenzyme by the Ca 2+ -pump protein was regarded as an important index of the purification of sarcoplasts.
Journal ArticleDOI
Calcium release and ionic changes in the sarcoplasmic reticulum of tetanized muscle: an electron-probe study.
TL;DR: The unchanged distribution of a permeant anion, chloride, argues against the existence of a large and sustained transSR potential during tetanus, if the chloride permeability of the in situ SR is as high as suggested by measurements on fractionated SR.
References
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Journal ArticleDOI
Adenosine triphosphate-linked concentration of calcium ions in a particulate fraction of rabbit muscle
Setsuro Ebashi,Fritz Lipmann +1 more
TL;DR: ATPase and ATP-dependent calcium ion concentration was studied with a membrane fraction isolated from homogenized rabbit skeletal muscle by differential centrifugation, indicating that it consists mainly of resealed tubules and vesicles of the endoplasmic reticulum.
Journal ArticleDOI
Sarcoplasmic reticulum. i. the uptake of ca++ by sarcoplasmic reticulum fragments.
A. Martonosi,R. Feretos +1 more
Journal Article
[The calcium pump of the "relaxing granules" of muscle and its dependence on ATP-splitting].
Book ChapterDOI
Energized Calcium Transport and Relaxing Factors
TL;DR: The energized calcium transport is described and the relaxing factors are discussed and the behavior of actomyosin in vitro and its correlation to in vivo contraction and relaxation of actonomyosin is discussed.
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Sarcoplasmic reticulum. i. the uptake of ca++ by sarcoplasmic reticulum fragments.
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