ION TRANSPORT IN LIVER MITOCHONDRIA - ENERGY BAERRIER AND SOICHEOMETRY OF AEROBIC K+ TRANSLOCATION

The relationship between translocation of K+ and respiration has been studied under conditions where large variations of the transmembrane K+ concentration gradient were obtained. It is found that the energy expenditure is a function of the number of ions translocated and not of the transmembrane concentration gradient. The K+/∼ ratio is slightly below 3 when measured on the total oxygen uptake and between 3 and 4 when measured on the Δ oxygen uptake. The maximal [K+]i/[K+]o ratio maintained by respiring liver mitochondria is about 1,600 corresponding to an equilibrium potential of 192 mV. When the [K+]i/[K+]o ratio exceeds 2,000 times addition of valinomycin under aerobic conditions causes an efflux instead of an uptake of K+. Mitochondria behave as perfect osmometers in a wide range of osmolarities. It can be calculated that the concentration of osmotically active internal K+ corresponds to 45% of the total osmolarity of the medium. Copyright © 1969, Wiley Blackwell. All rights reserved