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| • |
Calcium
regulation is vital
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| • |
In
smooth muscle, the cytosolic free Ca2+ concentration is ~ 0.1 mM in basal
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state; ~ 10,000
times lower than that present in the extracellular space (mM)
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Activation of
cells induces an increase in cytosolic concentration up to ~1-10
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mM.
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Ca2+
diffuses in cell much more slowly than predicted from its small volume;
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Ca2+
atom migrate 0.1-0.5 mm, lasting only ~ 50 ms before being bound.
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Ca2+
used by different vasoactive agents comes from extracellular and/or
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intracellular
space.
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Intracellular
Ca2+ is localized in the mitochondria and SR
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Location is most
important
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