THYROXINE INDUCES CYCLOSPORINE A-INSENSITIVE, CA2-DEPENDENT REVERSIBLE PERMEABILITY TRANSITION PORE IN RAT-LIVER MITOCHONDRIA()

The effect of thyroxine on Ca2+-dependent mitochondrial permeability t ransition has been examined, It is shown that 40 mu M thyroxine induce s high amplitude swelling and decrease in membrane potential in Ca2+-l oaded rat liver mitochondria, both in the presence and absence of cycl osporin A. Thyroxine-induced decrease in membrane potential is partial ly or completely reversed by addition of EGTA into the incubation medi um, Nigericin and ADP are shown to prevent, or significantly delay, th e effects of thyroxine on both mitochondrial swelling and membrane pot ential, whereas nicotinamide potentiates the permeabilisation of mitoc hondria, It is suggested that thyroxine induced reversible, cyclospori n A-insensitive permeability transition pore (PTP) opening in the inne r mitochondrial membrane. (C) 1997 Federation of European Biochemical Societies.