Intracellular distribution of copper and zinc in the liver of copper-exposed cattle from northwest Spain.

The intracellular distribution of copper (Cu) and zinc (Zn) in the livers of normal and moderately Cu-exposed cattle was investigated with the aim of improving understanding of the pathophysiology of Cu accumulation in cattle. At total liver Cu concentrations within the generally accepted normal range (25-100 mg/kg fresh weight) the large-granule fraction was the main subcellular compartment for Cu accumulation, followed by the cytosol and the nucleus, whereas in the microsomal fraction Cu accumulation was very low. With increasing Cu exposure, the capacity of the large-granule fraction to accumulate Cu decreased, proceeding towards a plateau (estimated at about 80 mg/kg at a projected total liver Cu concentrations of 450 mg/kg), accompanied by progressively greater Cu accumulation in the nucleus and cytosol.