Nigericin-induced transient changes in rat-liver mitochondria.

Addition of nigericin to mitochondria oxidizing succinate in a choline- and Tris-supplemented, low-KCl medium leads to a transient matrix acidification, followed by a return of pHin to values very close to pHout. The initial inhibition of stimulated respiration is gradually relieved as pHin returns to higher values. Matrix realkalinization depends on the operation of the H+ pumps and on the electrogenic influx of cations and efflux of anions. The process leads to replacement of much of the matrix K+ by other cations. Throughout the acidification/realkalinization cycle delta mu H variations, if any, are small, even though there are profound changes in the relative contributions of its two components, delta psi and delta pH.