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Copper‐associated liver disease in North Ronaldsay sheep: a possible animal model for non‐Wilsonian hepatic copper toxicosis of infancy and childhood

Indian childhood cirrhosis (ICC), endemic Tyrolean infantile cirrhosis (ETIC) and idiopathic copper toxicosis (ICT), are clinically and pathologically indistinguishable liver disorders of infants and young children linked with exogenous copper and with increasing evidence for a genetic predisposition. North Ronaldsay sheep are a primitive breed which have adapted to a copper impoverished environment (<5 ppm) and display an abnormal sensitivity to copper poisoning when transferred to a copper replete (11 ppm) habitat. The aetiological parallels prompted a study of copper‐associated liver disease in North Ronaldsay sheep (RCT) to see if the pathology could contribute to the understanding of the childhood disorder. A retrospective study was performed in which the livers of 22 mainland‐bred North Ronaldsay sheep were compared with three island‐bred sheep and categorized for liver copper content and pathomorphology. It was found that all the mainland sheep had accumulated liver copper (>300 µ/g), in contrast to the island sheep, although 10 sheep with increased liver copper (mean 600 SD 270 µ/g) showed no evidence of liver damage. A further 10 sheep with liver copper (mean 1276 SD 508 µg/g) exhibited periportal to panlobular histochemical copper retention, a periportal and/or panlobular pericellular fibrosis, a mixed inflammatory infiltrate and cholangioplasia. Steatosis was absent and regeneration was in abeyance. Finally, two sheep (liver copper>2000 µg/g) had a more active hepatitis with a florid pericellular, panlobular fibrosis and cirrhosis. Electron microscopy identified large numbers of collagen‐producing hepatic stellate (Ito) cells in periportal regions. The pathological findings were sufficiently reminiscent of ICC, ETIC and ICT to warrant further exploration of RCT as a putative animal model. The North Ronaldsay sheep liver may be a useful tool for the investigation of copper‐induced fibrogenesis. Copyright © 2001 John Wiley & Sons, Ltd.