Abstract
After intravenous administration of Na2 51CrO4 to rats the subcellular distribution of51Cr was determined at different time intervals after dosage. A time-related compartment shift from the cytosol into the mitochondrial and nuclear fractions was demonstrated. Dialysis studies indicated a firmer binding of51Cr to the mitochondrial and nuclear fractions than to the cytosol. Indirect evidence is presented that reduction from CrVI to CrIII takes place primarily inside the mitochondria. The hypothesis is put forward that reduction from CrVI to CrIII may take place at any intracellular site where electron donors are available. Electron donors in the different intracellular organelles are discussed.