Establishment and characterization of methylmercury-resistant PC12 cell line

Methylmercury (MeHg)-resistant sublines of rat pheochromocytoma (PC12) cells were isolated by repeated exposure to stepwise increased concentrations of MeHg. One of the sublines (PC12/TM) showed an 8- to 10-fold increase in resistance to MeHg compared with parent PC12 cells on the basis of the concentration required for 50% inhibition (IC50) of growth. PC12/TM cells accumulated smaller amounts of MeHg than parent PC12 cells. This reduction in MeHg accumulation in PC12/TM cells resulted from slow uptake and rapid efflux. The intracellular glutathione (GSH) level in PC12/TM cells was four times higher than that of PC12 cells. Pretreatment of PC12/TM cells with buthionine sulfoximine, which decreased the GSH level to that of the parent PC12 cells, increased the sensitivity of PC12/TM cells to MeHg. A close correlation between the MeHg accumulation and MeHg sensitivity was found among seven sublines of PC12 cells and parent PC12 cell line. The GSH level in PC12 sublines was also correlated with their sensitivity to MeHg.