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THE ACCUMULATION OF CALCIUM IONS BY SARCOTUBULAR VESICLES

M E CARSTEN, W F MOMMAERTS

    The Journal of General Physiology
    |November 1, 1964
    PubMed

    Insights

    Rabbit skeletal muscle microsomes accumulate calcium and split nucleoside triphosphates, showing specific nucleotide preferences. Various compounds affect calcium uptake and ATPase activity, offering insights into muscle relaxation and oxidative phosphorylation.

    Area of Science:

    • Muscle Physiology
    • Biochemistry
    • Cellular Biology

    Background:

    • Sarcotubular preparations are crucial for studying muscle contraction and relaxation.
    • Calcium ion (Ca++) accumulation is a key process in muscle relaxation.
    • Nucleoside triphosphate hydrolysis powers cellular functions, including muscle activity.

    Purpose of the Study:

    • To investigate the nucleotide specificity of Ca++ accumulation and ATP hydrolysis in rabbit skeletal muscle microsomes.
    • To examine the effects of various chemical agents on the Ca++ pump and associated ATPase activity.
    • To explore the relationship between Ca++ uptake, ATPase activity, and muscle relaxing factor (MRF) activity.

    Main Methods:

    • Utilized rabbit skeletal muscle microsomal preparations.
    • Measured Ca++ accumulation in the presence of oxalate.
    • Assessed nucleoside triphosphate splitting (ATPase activity).
    • Tested the effects of caffeine, pyridoxalphosphate, carnosine, thiourea, p-chloromercuribenzoate, iodoacetate, atabrine, dinitrophenol, amytal, oligomycin, rutamycin, and antimycin A.

    Main Results:

    • Demonstrated nucleotide specificity for both Ca++ accumulation (ATP > GTP, CTP, ITP > UTP) and ATP hydrolysis (ATP > ADP > ITP > GTP > CTP > UTP).
    • Identified inhibitors of the Ca++ pump and ATPase, including pyridoxalphosphate, thiourea, p-chloromercuribenzoate, atabrine, dinitrophenol, and amytal.
    • Observed differential effects of oligomycin, rutamycin, and antimycin A on Ca++ uptake and ATPase activity.
    • Noted discrepancies between Ca++ uptake and relaxing factor activities.

    Conclusions:

    • The study elucidates the biochemical characteristics of the sarcoplasmic reticulum's calcium pump and its nucleotide preferences.
    • Results suggest potential links between these processes and partial reactions in oxidative phosphorylation.
    • The distinct behaviors of Ca++ uptake and relaxing factor activities indicate the involvement of multiple components in muscle relaxation beyond the primary calcium pump.
    Keywords:
    ADENINE NUCLEOTIDESADENOSINE TRIPHOSPHATASEAMOBARBITALANTIBIOTICSANTIMYCIN AARSENICCAFFEINECALCIUMCHLOROMERCURIBENZOATESDINITROPHENOLSEXPERIMENTAL LAB STUDYIODOACETATESMETABOLISMMICROSOMESMUSCLE PROTEINSNUCLEOTIDESOXALATESPEPTIDESPHARMACOLOGYPHOSPHATESPOTASSIUMPYRIDOXAL PHOSPHATEQUINACRINERABBITSSODIUMSULFHYDRYL COMPOUNDSTHIOUREA

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