The dominant mode of cell death in cardiomyocytes under acute ischemic insult, either necrosis or apoptosis, remains to be clearly shown.

Cultured neonatal rat ventricular myocytes (NRVM) were incubated under hypoxic (mixture gas of 95%N2/5%CO2 in glucose containing media), ischemic (hypoxia plus glucose depletion in the media), ischemic and acidic conditions (ischemia with media pH 7.1). The level of cell death was assessed by trypan blue staining. To differentiate the mode of cell death, genomic DNA extraction and electrophoresis, Annexin V/propodium iodide staining, western blot for caspase activation and transmission electron microscopy were employed.

The number of cell deaths in the NRVM cultured under hypoxic conditions was similar to that of the controls. The rate of cell death was significantly increased in the NRVM cultured under ischemic conditions, and was accelerated further in an acidic milieu, which simulated the accumulation of metabolic byproducts in ischemia. No signs of apoptotic cell death were observed in the NRVM cultured under ischemic conditions. The morphological examination of the cells in ischemia mostly revealed necrotic death.

The presence of glucose protected the cardiomyocytes from cell death under hypoxic conditions. Incubation of the NRVM in ischemia resulted in increased cell deaths, which was accelerated in an acidic milieu. In our model of acute ischemia, without reoxygenation, the cardiomyocyte cell deaths appeared to be primarily induced via necrosis rather than apoptosis.