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  • Title: Ca2+ uptake coupled to glycogen phosphorolysis in the glycogenolytic-sarcoplasmic reticulum complex from rat skeletal muscle.
    Author: Nogues M, Cuenda A, Henao F, Gutiérrez-Merino C.
    Journal: Z Naturforsch C J Biosci; 1996; 51(7-8):591-8. PubMed ID: 8810099.
    Abstract:
    The glycogenolytic-sarcoplasmic reticulum complex from rat skeletal muscle accumulates Ca2+ upon stimulation of glycogen phosphorolysis in the absence of added ATP. It is shown that an efficient Ca2+ uptake involves the sequential action of glycogen phosphorylase, phosphoglucomutase and hexokinase, which generate low concentrations of ATP (approximately 1-2 microM) compartmentalized in the immediate vicinity of the sarcoplasmic reticulum Ca2+, Mg(2+)-ATPase (the Ca2+ pump). The Ca2+ uptake supported by glycogenolysis in this subcellular structure is strongly stimulated by micromolar concentrations of AMP, showing that the glycogen phosphorylase associated with this complex is in the dephosphorylated b form. The results point out that the flux through this compartmentalized metabolic pathway should be enhanced in physiological conditions leading to increased AMP concentrations in the sarcoplasm, such as long-lasting contractions and in ischemic muscle.
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