Active Transport of Potassium Ion in Heart Mitochondria
Several factors affecting K+ transport by rabbit heart mitochondria were examined, using a K+-sensitive electrode. The histone fractions f2a and β-7 produced an energy-dependent efflux of K+. Inorganic phosphate was required for optimal activity; Km for phosphate was 60 µM. Both rate and extent of K+ efflux decreased as K+ concentration in the reaction medium was increased. The direction of valinomycin-induced K+ movements was shown to depend on the net resultant of an active transport mechanism and increased membrane permeability. The detergent triton X-100 produced a nonspecific increase in membrane permeability that led to a rapid efflux of K+. Evidence is presented for competition between ion transport and ATP formation for some common energy intermediate. Possible mechanisms of action of histones and other agents affecting heart mitochondrial K+ transport are considered.
- Accepted May 4, 1967.
- © 1967 American Heart Association, Inc.