Abnormal Hepatic Copper Storage in a Teleost Fish (Morone americana)

Abstract

Excessive copper storage in livers of feral white perch (Morone americana) from the Chesapeake Bay is described. Age-related, progressive accumulation of hepatic copper in levels often exceeding 1,000 μg/g wet weight was associated with peribiliary fibrosis and inflammation, bile duct hyperplasia, prominent, enlarged melanomacrophage centers, and disruption of hepatic architecture in older fish. Levels of zinc were mildly elevated compared to striped bass (Morone saxitilis) and adult rats. Cholangiomas were found in two perch. Rubeanic acid-stained liver had abundant copper-positive cytoplasmic granules in hepatocytes and cells of melanomacrophage centers. Subcellular fractionation showed that 90% of hepatocellular copper was in nuclei/ cell debris fractions (which also contain tertiary lysosomes). Using electron probe microanalysis, high copper levels were localized in hepatocellular cytoplasmic bodies. Resolution of hepatic cytosol by gel permeation chromatography indicated that approximately 50% of the cytosolic copper in the white perch was bound to non-specific high molecular weight proteins, with the remaining 50% eluting at a peak where rat metallothionein is located. Ultrastructural examination revealed abundant lysosomes, increased size and number of peroxisomes, and increased density and numbers of mitochondrial matrix granules. This study indicates that white perch may be a model for studying effects of excessive copper accumulation and cellular mechanisms which control copper kinetics.