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Effects of low extracellular calcium on cytosolic calcium and ischemic contracture

E Jimenez1, P del Nido, M Sarin

  • 1Department of Surgery, University of Illinois, Chicago.

The Journal of Surgical Research
|September 1, 1990
PubMed

Insights

Low extracellular calcium reduces myocardial contracture during ischemia. This intervention attenuates the rise in intracellular calcium, delaying injury and decreasing contracture force in rabbit hearts.

Area of Science:

  • Cardiovascular Physiology
  • Ischemic Heart Disease Research
  • Calcium Homeostasis

Background:

  • Myocardial cytosolic calcium ([Cai]) increases during ischemia, preceding irreversible contracture.
  • Membrane-bound calcium stores are depleted concurrently with the [Cai] rise.

Purpose of the Study:

  • To investigate the effect of low extracellular calcium ([Cao]) on ischemia-induced myocardial contracture.
  • To determine if low [Cao] can mitigate the detrimental rise in intracellular calcium during ischemia.

Main Methods:

  • Isolated retroperfused rabbit hearts subjected to 37°C ischemia.
  • Perfusion with low extracellular calcium (100 μM) versus normal calcium (2.45 mM).
  • Measurement of intracellular calcium ([Cai]) using Fura-2 AM fluorescent indicator.

Main Results:

  • Low [Cao] perfusate significantly decreased peak contracture pressure.
  • Low [Cao] delayed the onset and peak of ischemic contracture.
  • In normal calcium, [Cai] rose >50% during ischemia; in low [Cao], [Cai] was attenuated and delayed.

Conclusions:

  • Low extracellular calcium (100 μM) attenuates ischemia-induced intracellular calcium rise.
  • Pre-ischemic low calcium perfusion delays contracture onset and reduces its force.
  • This suggests a protective role for low extracellular calcium in preventing irreversible ischemic injury.

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