Recovery from calcium-induced damage in a neuroblastoma cell line

Abstract

Calcium may act as a second messenger in normal cellular signal transduction systems. However, an excessive influx of calcium into the cytoplasm is well known to be a final common pathway causing cell death under various pathological conditions. The purpose of this study was to investigate the effect of a transient treatment with the calcium ionophore A23187 on the recovery process of cell viability, energy metabolsim, amino acid incorporation and calcium uptake in a neuroblastoma cell line. When neuroblastoma cells were treated with 20 μM of the calcium ionophore A23187 in combination with extracellular calcium, rapid energy failure and marked inhibition of amino acid incorporation by the cells occurred together with a massive influx of calcium, and finally resulted in cell death. Recovery from this calcium-induced damage with regards to energy metabolism and prognosis of cell viability was better after a 10-min treatment than after a 30-min treatment with A23187. After a 10-min treatment, the viability was higher in calcium-free medium than in calcium-containing medium in contrast with the cases after treatment for 30 min. The above difference in viability after treatment for 10 min had a very significant correlation with the degree of exclusion of excessive calcium and the recovery of CTP, indicating that the recovery of CTP and the rate of calcium exclusion may be final markers of the recovery of cells from calcium-induced damage rather than the recovery of ATP or amino acid incorporation. Amino acid incorporation was restricted to a level lower than that of the control long after the recovery of GTP and the GTP/GDP ratio. This may indicate that the incorporation of amino acids by the cells for protein synthesis is the aspect most vulnerable to calcium overload.