Role of mitochondria in control of calcium content of liver slices

Abstract

INTRACELLULAR Ca²⁺ is thought to be important in the control of metabolic activity^1,2. In liver cells, three energy-dependent transport activities capable of modifying the cellular distribution of this ion have been described—its accumulation by mitochondria^3,4 and endoplasmic reticulum⁵ and its extrusion from the cell^6,7. Mutual interactions, however, between these activities and their relative importance in determining total cell Ca²⁺ have so far been little studied in intact cells. One reason for this has been the difficulty of avoiding redistribution of Ca²⁺ between organelles when the cells are broken for isolation procedures, although Chen et al.⁸ used ruthenium red, added to the homogenisation medium, to prevent such redistribution in crab hepatopancreas. We now show that redistribution of Ca²⁺ into the mitochondria of rat liver can also be largely prevented by adding La³⁺ (another inhibitor of mitochondrial Ca²⁺ transport; ref. 9) to the homogenisation medium. We have also studied the contribution of mitochondria to the Ca²⁺ content of rat liver slices incubated in conditions in which total cell Ca²⁺ varies greatly.