Cellular injury of primary cultures of rat myocytes incubated in calcium-free medium followed by recovery in calcium

Primary monolayer cultures of rat myocardial cells were used to study the cellular injury that occurs when calcium is reintroduced after a period of calcium depletion. Cultures were treated with a calcium-free balanced salt solution (BSS) for 2 h and were then incubated for different time periods in the presence of normocalcemic BSS (2.5 m M CaCl₂). Myocyte calcium content was determined after the calcium-free period and after incubation in the presence of calcium. Leakage of cytoplasmic lactate dehydrogenase (LDH) into the medium was used as an index of cell injury. At the end of the calcium-free period there was a significant decrease in the total cellular content of calcium, and LDH release was minimal. After incubation in normocalcemic BSS, the myoctte calcium content increased progressively with time and cellular injury was manifested by significant leakage of LDH. The calcium content of treated cells reached control levels 10 min after calcium repletion. Maximal keakage of LDH was observed 60 min after the restoration of calcium. The calcium content of treated cultures was higher than that of control cultures 120 min after incubation in normocalcemic BSS.