Control of mitochondrial Ca2+ retention by ADP-stimulated glutamic dehydrogenase

The protective effect of ADP on unspecific Ca²⁺ release and collapse of the transmembrane potential was analyzed in mitochondria from kidneys of rats. The presence of ADP in the incubation mixture prevents Ca²⁺ leakage and collapse of in sucrose-containing medium, but fails to do so in KCl medium. The effect of the adenine nucleotide in sucrose media correlates with an increase in the level of reduced pyridine nucleotides; the increase was due to a stimulatory effect on the activity of glutamic dehydrogenase. It also was observed that in KCl media, in the presence and in the absence of ADP the rate of NADH oxidation through the respiratory chain was higher than in sucrose; in this latter medium a high level of reduced pyridine nucleotides was found, in comparison to KCl media. It is proposed that the role of ADP is to increase glutamic dehydrogenase activity and in consequence to provoke a higher rate of formation of NADH which in turn controls Ca²⁺ release.