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Related Experiment Videos

Matrix free Ca2+ in isolated chromaffin vesicles.

D Bulenda, M Gratzl

    Biochemistry
    |December 17, 1985
    PubMed
    Summary

    Secretory vesicles in the adrenal medulla accumulate calcium ions, exchanging them for protons. This process is crucial for regulating intracellular calcium levels and vesicle function.

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    Gamma-aminobutyric acid (GABA): a para- and/or autocrine hormone in the pituitary.

    FASEB journal : official publication of the Federation of American Societies for Experimental Biology·2001

    Area of Science:

    • Biochemistry
    • Cell Biology
    • Neuroendocrinology

    Background:

    • Secretory vesicles store neurotransmitters and hormones.
    • Calcium ions (Ca2+) play critical roles in cellular signaling and vesicle exocytosis.

    Purpose of the Study:

    • To investigate the mechanism of calcium (Ca2+) and magnesium (Mg2+) ion transport in isolated bovine adrenal medulla secretory vesicles.
    • To elucidate the role of the proton gradient in regulating intravesicular Ca2+ concentration.

    Main Methods:

    • Isolation of secretory vesicles from bovine adrenal medulla.
    • Measurement of Ca2+ and Mg2+ content using Ca2+-selective electrodes and atomic emission spectroscopy.
    • Monitoring proton (H+) movement via pH changes and 9-aminoacridine release.
    • Utilizing the proton ionophore A23187 to induce ion flux.

    Main Results:

    • Isolated vesicles contain significant amounts of Ca2+ and Mg2+.
    • Addition of A23187 promotes Ca2+ uptake coupled with proton (H+) release, indicating a proton-Ca2+ exchange mechanism.
    • The proton gradient (delta pH) is essential for substantial Ca2+ accumulation.
    • Intravesicular Mg2+ is not released by A23187.
    • Calculated intravesicular free Ca2+ concentration is approximately 24 microM.

    Conclusions:

    • Bovine adrenal medulla secretory vesicles actively transport Ca2+ via a proton-driven mechanism.
    • The proton gradient across the vesicle membrane is a key regulator of intravesicular Ca2+ levels.
    • These findings contribute to understanding the regulation of catecholamine release and intracellular calcium homeostasis.

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