Copper and liver injury--experimental studies on the dogs with biliary obstruction and copper loading

Cytotoxic effect of excessive copper in the liver of the dogs with longstanding obstructive jaundice were investigated. Common bile duct was ligated in adult mongrel dogs for a period of 21 to 93 days. Copper (0.5 mg/kg weight, every other day) was administered intravenously. Copper content and morphologic changes of the liver was compared with those of the common bile duct ligated dogs without copper administration and of the normal control. Liver copper content was quantitated by atomic absorption spectrophotometry and morphologic investigation was carried out ultrastructurally and histochemically (dimethylaminobenzylidine rhodanine stain for copper and orcein stain for copper associated protein). The copper content of the liver was 57 +/- 8.75 microgram/g wet weight (mean +/- S.E.) in the normal control, 80.84 +/- 15.76 in the common bile duct ligated dogs and 463.46 +/- 76.42 in the common bile duct ligated dogs with copper administration. There was a significant increase (p less than 0.01) of the liver copper content in the common bile duct ligated dogs with copper administration but not in the common bile duct ligated dogs without it. Histologically, the liver showed changes of longstanding cholestasis and of early biliary cirrhosis in the dogs over three months after ligation. Ultrastructurally, both groups showed dilatation of bile canaliculi with decreased and swollen microvilli protruding into their lumina, expanded pericanalicular ectoplasm with increased microfibrils and various forms of intracanalicular and intracytoplasmic bile assuming myelin-figure, crystalloid and dense-amorphous appearances. Also present were increased and dilated smooth-surfaced endoplasmic reticulum, mitochondria showing curled cristae with electron dense ground substance and decreased microvillous projections of hepatocyte cell membranes into Disse's space. Only significant morphologic difference between two groups was the presence of copper-protein complex demonstrated by rhodanine and orcein stains as intracytoplasmic coarse granules in the common bile duct ligated dogs with copper administration. These copper-protein complex granules correspond to partially membrane-bound dense bodies seen ultrastructurally, which probably represent autophagic vacuoles or lysosomal residual bodies. Above result suggests that excessive copper accumulated in the liver as lysosomal bodies in longstanding extrahepatic biliary obstruction with copper loading does not produce significant liver cell injury despite eight fold increase of the liver copper content.