Copper toxicosis and tolerance in the rat. III. Intracellular localization of copper in the liver and kidney.

Male rats fed a 3 g/kg copper diet were killed sequentially up to 14 weeks. Copper in liver and kidney cortex was identified histochemically and assayed in homogenates and gradient fractions following analytical subcellular fractionation on reorientating sucrose density gradients. Copper accumulated fastest in the liver postnuclear (PNS) supernatant fraction which became saturated at 2 weeks; there was a distinct localization of copper in hepatic lysosomes which displayed progressively enhanced fragility. Rapid accumulation of copper then occurred in liver and kidney nuclear (N) fractions, peak copper concentrations coinciding with hepatic and renal tubular necrosis. Copper accumulated slowly up to 4 weeks and was maintained to 14 weeks in the cytosol of the proximal renal tubules from which it appeared to be excreted. Subsequently liver copper declined in both liver fractions and kidney (N) fractions; hepatic lysosomes regained stability, regeneration of liver and kidney occurred, and the rats were tolerant to continued copper administration. These findings do not support a primary role for copper-loaded lysosomes in the genesis of cell injury, but suggest that nuclear saturation may be the destabilizing event. Recovery is associated with changes in the subcellular distribution of copper within liver and kidney and renal excretion of excess.