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Old 12-21-2015
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Default Calcium- extracellular or intracellular?

Is calcium an extracellular or intracellular ion?
I thought it was intracellular but I read on Uworld that cytoplasmic calcium accumulation is a hallmark of ischemic injury. Could someone please explain?
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Old 12-21-2015
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Originally Posted by datson View Post
Is calcium an extracellular or intracellular ion?
I thought it was intracellular but I read on Uworld that cytoplasmic calcium accumulation is a hallmark of ischemic injury. Could someone please explain?
Calcium has a very high concentration gradient. Cytoplasm has almost no calcium. Calcium is either stored in the smooth endoplasmic reticulum or is pumped outside. Cytoplasmic calcium accumulation is pathologic.

Calcium accumulation is the hallmark of irreversible cell injury. Ca2+ pumps require ATP. No ATP=no pump activity=Ca2+ stays in the cytoplasm and causes damage.
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Old 12-22-2015
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Originally Posted by Nodo View Post
Calcium has a very high concentration gradient. Cytoplasm has almost no calcium. Calcium is either stored in the smooth endoplasmic reticulum or is pumped outside. Cytoplasmic calcium accumulation is pathologic.

Calcium accumulation is the hallmark of irreversible cell injury. Ca2+ pumps require ATP. No ATP=no pump activity=Ca2+ stays in the cytoplasm and causes damage.
Just to add a little more, calcium activates a bunch of enzymes, which may not be good for the cell, if in excess. So it's only natural for the cell to either - sequester it inside a binding protein (like, say calmodulin) or to pump it out. Ionised calcium is mostly extracellular.
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