[Changes in the effect of Cd2+ on the respiration of isolated rat liver mitochondria after their preincubation with Ca2+, Sr2+, Ba2+, Mn2+ and ruthenium red].

Action of Cd+ on mitochondrial respiration is decreased by some bivalent ions, however the reason of this still remains obscure. Change of Cd2+ action over a wide range of its concentrations on respiration of rat liver mitochondria in states 4, 3 and in the presence of 2, 4-dinitrophenol (DNP) after mitochondrial preincubation with Ca2+, Sr2+, Ba2+, Mn2+ or ruthenium Red (RR) was studied in vitro. In the control (experiments without preincubation), Cd2+ lowers mitochondrial respiration in state 3 as well as that in the presence of DNP, and increases the respiration in state 4. However, the respiration is decreased if Cd2+ concentrations are more than 15 microM; in this case a short-term activation of respiration appears. In comparison with the control, it was demonstrated that the action of Cd2+ on mitochondrial respiration was enhanced in experiments with Ca2+, decreased in experiments with Sr2+ and Mn2+, and did not vary practically in experiments with Ba2+. The activation of respiration in state 4 is increased in experiments with Ca2+ and is absent with Mn2+. Different changes in Cd2+ action on mitochondrial respiration in experiments with Me2+ ions are associated with their influence on mitochondrial membrane permeability, as well as with magnitude of the ion radius. The maximum reduce of Cd2+ action was achieved in experiments with RR, except that respiration in state 3 decreased by Cd2+ to 30 microM more rapidly than with Sr2+ and Mn2+. Under RR experiments the mitochondrial respiration in the presence of DNP as well as that in state 3 is linearly decreased (up to 15 microM Cd2+). A discussion involves issues of Cd2+ transport into the matrix, under uniporter blocking, as well as inorganic phosphate influence on Cd2+ effects, location of regulatory centers of ion permeability and location of active group of respiration enzymes.