A COMPARISON OF EFFECTS OF DIFFERENT DIVALENT CATIONS ON A NUMBER OF MITOCHONDRIAL REACTIONS LINKED TO ION TRANSLOCATION

Ca2+, Sr2+, Mg2+, Mn2+, Ba2+, and Be2+ behave differently with respect to their effects on activation of respiration, proton ejection, and K+ movements across the membrane of isolated rat liver mitochondria. The metal ions tested can be divided into three groups: (1) Mg2+ and Be2+ have no effect on either respiration, H+ ejection, or K+ movements. (2) Mn2+ and Ba2+ induce a slow activation of respiration and proton ejection. These ions exchange with mitochondrial K+ also in the absence of valinomycin; this exchange is out of phase with respect to proton ejection. (3) Ca2+ and Sr2+ promote an extremely rapid extra-oxygen consumption accompanied by H+ output. Ca2+ can exchange with mitochondrial K+ only when the membrane is rendered permeable to K+ by valinomycin. © 1969.