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Updated: Aug 18, 2026

Measurement of Calcium Fluctuations Within the Sarcoplasmic Reticulum of Cultured Smooth Muscle Cells Using FRET-based Confocal Imaging
10:05

Measurement of Calcium Fluctuations Within the Sarcoplasmic Reticulum of Cultured Smooth Muscle Cells Using FRET-based Confocal Imaging

Published on: June 20, 2016

Chemical modification of sarcoplasmic reticulum with methylbenzimidate. Stimulation of Ca2+ efflux

V Shoshan-Barmatz

    The Biochemical Journal
    |April 1, 1987
    PubMed

    Insights

    Methylbenzimidate (MBI) treatment of sarcoplasmic reticulum membranes stimulates ATP hydrolysis and inhibits calcium (Ca2+) accumulation. MBI modifies a protein factor, enhancing Ca2+ release, not the Ca2+-ATPase itself.

    Area of Science:

    • Biochemistry
    • Cell Biology
    • Membrane Protein Function

    Background:

    • Sarcoplasmic reticulum Ca2+-ATPase (SERCA) is crucial for muscle contraction by pumping Ca2+ into the SR.
    • Understanding regulatory mechanisms of Ca2+ transport is vital for muscle physiology.

    Purpose of the Study:

    • To investigate the effect of methylbenzimidate (MBI) on sarcoplasmic reticulum (SR) membrane function.
    • To determine if MBI affects Ca2+ ATPase activity or other regulatory components.

    Main Methods:

    • Treatment of SR membranes with MBI in the presence of ATP and varying nucleotides.
    • Assays for ATP hydrolysis, Ca2+ accumulation, and Ca2+ release.
    • Proteoliposome reconstitution with purified and partially purified Ca2+-ATPase.

    Main Results:

    • MBI treatment significantly stimulated ATP hydrolysis and inhibited Ca2+ accumulation.
    • Nucleotide presence was essential for MBI's effect, with specific order of potency.
    • MBI-treated membranes showed rapid Ca2+ release, unlike controls.
    • MBI affected partially purified ATPase but not purified ATPase, suggesting modification of a non-ATPase factor.

    Conclusions:

    • MBI in the presence of ATP stimulates Ca2+ release from SR membranes.
    • This effect is mediated by modification of a protein factor distinct from the (Ca2+ + Mg2+)-ATPase.
    • MBI provides a tool to probe regulatory mechanisms of SR Ca2+ handling.

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