A study of calcium pump activity of lysosomes from rat renal cortex

Fractions rich in either primary or secondary lysosomes were prepared from rat renal cortex by differential centrifugation and evaluated for their capacity for net calcium uptake. No uptake was observed in the absence of ATP. A vigorous uptake did take place in the presence of ATP but it was largely prevented by azide and other inhibitors of mitochondrial calcium uptake, suggesting that it was attributable to contamination by mitochondria. Evidence was obtained for an inhibitory influence of the secondary lysosomal fraction on mitochondrial calcium uptake.