Control of the pyridine nucleotide-linked Ca 2+ release from mitochondria by respiratory substrates

Abstract

Oxidation of mitochondrial pyridine nucleotides followed by their hydrolysis promotes Ca 2+ release from intact liver mitochondria. In most of the previous studies oxidation was achieved with pro-oxidants which were added to mitochondria respiring on succinate in the presence of rotenone, a site I-specific inhibitor of the respiratory chain. Here we investigate pro-oxidant dependent and independent Ca 2+ release from mitochondria when respiration is supported either by the NAD +-linked substrate β-hydroxybutyrate, or by succinate. In the presence, as well as in the absence, of the pro-oxidant t-butylhydroperoxide mitochondria retain Ca 2+ much better with succinate than with β-hydroxybutyrate, as respiratory substrate. When Ca 2+ release is induced by t-butylhydroperoxide succinate-supported Ca 2+ retention is impeded by rotenone. Ca 2+ release (pro-oxidant dependent or independent) is paralleled by oxidation and hydrolysis of intramitochondrial pyridine nucleotides, and Ca 2+ retention is paralleled by reduction of pyridine nucleotides. It is concluded that the pyridine nucleotide-linked Ca 2+ release from mitochondria can be controlled by respiratory substrates which regulate the intramitochondrial hydrolysis of oxidized pyridine nucleotides.