What question did this study set out to answer?

To determine how varying magnesium concentrations regulate calcium movement between the sarcoplasmic reticulum and the myofilament space in skinned muscle fibers.

January 1, 1977The Journal of General PhysiologyOpen Access

Regulation by magnesium of intracellular calcium movement in skinned muscle fibers.

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Why the study?

Does varying magnesium concentration alter intracellular calcium movement in skinned muscle fibers?

Key Points

To determine how varying magnesium concentrations regulate calcium movement between the sarcoplasmic reticulum and the myofilament space in skinned muscle fibers.
Measured isometric force as an indicator of myofilament space calcium in calcium-loaded skinned muscle fibers at 20°C in the presence of 5 mM ATP.
Assessed contraction and relaxation kinetics under varying magnesium concentrations ranging from 0.25 mM to 3 mM.
Examined the inhibition of sarcoplasmic reticulum calcium transport by introducing 0.5 mM cadmium.
Elevating magnesium from 1 mM to 3 mM strongly inhibited calcium-induced force spikes, slowed force development, and accelerated relaxation in calcium-free solutions.
Lowering magnesium to 0.25 mM induced phasic force transients in relaxed fibers, whereas increasing magnesium induced transient relaxation in contracting fibers.
Cadmium (0.5 mM) antagonized the relaxant and inhibitory effects of elevated magnesium, indicating that magnesium stimulates active calcium uptake by the sarcoplasmic reticulum.

Structured PICO

Does varying magnesium concentration alter intracellular calcium movement in skinned muscle fibers?

Population

Skinned muscle fibers

Intervention

Varying concentrations of magnesium (e.g., 3 mM Mg, 0.25 mM Mg)

Comparator

1 mM Mg

Outcome

Isometric force as an indicator of myofilament space (MFS) Casurrogate

Magnesium stimulates active calcium uptake by the sarcoplasmic reticulum in skinned muscle fibers, affecting local myofilament space calcium levels.

Discussion

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Implication

Skinned-fiber Mg effects on SR Ca uptake should not guide clinical Mg use; leaves open relevance to intact cardiomyocyte Ca regulation.

Cite This Study

Stephenson et al. (1977) studied this question.

synapsesocial.com/papers/6a709c81e36a167817e26a9a https://doi.org/10.1085/jgp.69.1.1

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Regulation by magnesium of intracellular calcium movement in skinned muscle fibers.

Key Points

Structured PICO

Discussion

Implication

Cite This Study

Regulation by magnesium of intracellular calcium movement in skinned muscle fibers.

Key Points

Structured PICO

Discussion

Implication

Cite This Study

Also Consider

Also Consider