STRONTIUM EXCITABILITY OF THE INNER MITOCHONDRIAL-MEMBRANE - REGENERATIVE STRONTIUM-INDUCED STRONTIUM RELEASE

Regenerative Sr++-induced Sr++ release from isolated rat liver mitocho ndria was studied using ion-selective electrode techniques. Mitochondr ia, when exposed to a pulse of Sr++, demonstrated a reversible and tra nsient increase in inner membrane permeability to K+ and H+ ions. The increase in permeability was an all-or-none process with a threshold d ependant on the amplitude of the Sr++ pulse. The threshold concentrati on of Sr++ was lowered from 120-150 mu M to 20-30 mu M when mitochondr ia were preloaded with 100 nmoles Sr++/mg protein. Release of matrix-s tored divalent cations provided a mechanism for amplification of the e xtramitochondrial Sr++ concentration (regenerative Sr++-induced Sr++ r elease). The mitochondrial inner membrane became refractory, since sub sequent cycles of excitation could not be immediately induced. These e xperiments demonstrate that the inner mitochondrial membrane is an exc itable membrane, with threshold-dependent, regenerative and subsequent ly refractile Sr++-induced Sr++ release characteristics.