['To assess any direct effect of extract of Paris polyphylla Simth (EPPS), a Chinese plant, on a cardiomyocyte subject to ischemia-reperfusion injury and to further elucidate its protective effect against myocardium ischemia on the cellular level.', 'Neonatal rat cardiomyocytes were isolated and subjected to an anoxia-reoxia injury simulating the ischemia-reperfusion injury in vivo in the presence or absence of EPPS or diltizem, a positive control. The lactate dehydrogenase (LDH) activities in culture supernatants and cell viabilities were analyzed using the enzymatic reaction kinetics monitoring-method and MTT method, respectively. Free intracellular calcium concentrations and activities of Na(+)-K(+) ATPase and Ca(2+) ATPase in cells were also measured with laser confocal microscopy and the inorganic phosphorus-transformation method, respectively.', 'In cardiomyocytes subject to anoxia-reoxia injury, EPPS at 50-400 mg/L showed a concentration-dependent inhibition on LDH leakage and maintenance of cell viability, and the effect was significant at 275 and 400 mg/L (both P<0.01). In addition, EPPS at 275 and 400 mg/L significantly inhibited the increase in intracellular free calcium (both P<0.01) as well as decreased the activities of Na(+)-K(+) ATPase and Ca(2+) ATPase (P<0.01, P<0.05).'] Does extract of Paris polyphylla Simth protect cardiomyocytes from anoxia-reoxia injury through inhibition of calcium overload?