COMPARISON BETWEEN THE EFFECTS OF THE MICROSOMAL CA-2+-TRANSLOCASE INHIBITORS THAPSIGARGIN AND 2,5-DI-(TERT-BUTYL)-1,4-BENZOHYDROQUINONE ON CELLULAR CALCIUM FLUXES

The effects of two inhibitors of the microsomal Ca2+-ATPase, thapsigargin and 2,5-di-(t-butyl)-1,4-benzohydroquinone, were compared in hepatocytes and in a T-cell line (JURKAT). Both compounds mobilized the same intracellular Ca2+ pool, which contained the Ins(1,4,5)P3-sensitive store, in hepatocytes and in JURKAT cells. The mobilization of the internal Ca2+ store with either compound activated Mn2+ entry in JURKAT cells, but not in hepatocytes. This suggests different properties of the bivalent-cation entry pathway between these cell types.