K+-dependent rebounds and oscillations in respiration-linked movements of CA++ and H+ in rat liver mitochondria.

Addition of Ca++ to rat liver mitochondria suspended in buffered 80 mM KC1 or NaCl causes activation of respiration, uptake of Ca++, and ejection of H+, followed by return of the respiratory rate to a resting steady state in which there are no further net movements of Ca++ and H+. However, when the KC1 concentration is only 20 mM, the Ca++-induced respiratory jump is followed by a period in which the resting respiration remains constant at a low resting rate, but in which the inverse Ca++-H+ exchange between mitochondria and medium undergoes oscillations. The oscillations are observed also after the accumulation of Sr++, but not after Mn++. They are maximal in media containing impermeant anions such as chloride, bromide, iodide, and thiocyanate. The oscillations are modified by buffer species and pH. Oscillations in the Ca++-H+ exchange do not occur in the presence of ATP, Mg++, sucrose, or permeant anions such as phosphate or acetate. The oscillations appear to depend in part on reverse electron flow from succinate to nicotinamide adenine dinucleotide. Since the mitochondria appear to behave in a self-correcting manner, the oscillations in the inverse Ca++ and H+ movements are rationalized in terms of a feedback relationship between Ca++ influx and efflux.