Effect of potential-dependent potassium uptake on calcium accumulation in rat brain mitochondria.

The effect of potential-dependent potassium uptake at 0-120 mM K on matrix Ca accumulation in rat brain mitochondria was studied. An increase in oxygen consumption and proton extrusion rates as well as increase in matrix pH with increase in K content in the medium was observed due to K uptake into the mitochondria. The accumulation of Ca was shown to depend on K concentration in the medium. At K concentration −30 mM, Ca uptake is decreased due to K-induced membrane depolarization, whereas at higher K concentrations, up to 120 mM K, Ca uptake is increased in spite of membrane depolarization caused by matrix alkalization due to K uptake. Mitochondrial K-channel blockers (glibenclamide and 5-hydroxydecanoic acid) diminish K uptake as well as K-induced depolarization and matrix alkalization, which results in attenuation of the potassium-induced effects on matrix Ca uptake, i.e. increase in Ca uptake at low K content in the medium due to the smaller membrane depolarization and decrease in Ca uptake at high potassium concentrations because of restricted rise in matrix pH. The results show the importance of potential-dependent potassium uptake, and especially the K channel, in the regulation of calcium accumulation in rat brain mitochondria. [ABSTRACT FROM AUTHOR]