Abstract
Intact perfused hearts subjected to calcium depletion and subsequent repletion undergo irreversible structural damage characterized by sarcolemmal disruption, hypercontracture, and the appearance of large electron dense deposits (thought to be calcium phosphate) within mitochondria. This structural damage is accompanied by increased intracellular Na+ and Ca++. Cultured embryonic chick heart cells subjected to the same conditions do not exhibit ultrastructural damage but do undergo similar ionic changes. This study characterizes the intracellular ionic changes associated with calcium repletion and assesses the role of mitochondria in the buffering of calcium.METHODS: Heart cells were obtained from 11-day-old chicken embryos and cultured as spherical aggregates for 3-4 days. The aggregates were then incubated at 37°C in HEPES buffered solution containing 1.3 mM Ca for 10 minutes (control period). Following this control period, the aggregates were incubated for 10 minutes in Ca-free HEPES buffer containing 1mM EGTA (depletion period). Finally, the aggregates were returned to normal, Ca-containing, HEPES buffer (repletion period).
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