Pivotal role of mitochondrial Ca2+ in microcystin-induced mitochondrial permeability transition in rat hepatocytes

We have shown earlier that microcystin-LR (MLR), a specific hepatotoxin, in duced onset of mitochondrial permeability transition (MPT) and apoptosis in rat hepatocytes. Here we attempted to investigate the role of mitochondria l Ca2+ in MLR-induced onset of MPT and cell death. Using confocal microscop y, we found that MLR caused an early surge of mitochondrial Ca2+ prior to t he onset of MPT and cell death. Pretreatment with 1,2-bis(O-aminophenoxyl)e thane-N,N,N ' ,N ' -tetracetic acid tetra(acetoxymethyl)ester (an intracell ular Ca2+ chelator) or ruthenium red (an inhibitor of mitochondrial Ca2+ un iporter) prevented the early mitochondrial Ca2+ surge and attenuated the su bsequent onset of MPT and cell death. On the other hand, a mitochondrial un coupler, CCCP, rapidly disrupted the mitochondrial membrane potential and a lso prevented the mitochondrial Ca2+ surge, onset of MPT, and cell death. W e thus conclude that mitochondrial Ca2+ plays an important role in the onse t of MPT and cell death in MLR-treated rat hepatocytes. (C) 2001 Academic P ress.