[Photometric determination of copper content in the liver during experimental chronic copper poisoning in sheep].

15 castrated rams were exposed to an oral copper-dosage of 3.64 mg/d/kg body weight for 84 days. The control group consisted of 11 rams with a copper intake of 0.14 mg/d/kg bodyweight. Liver biopsies were taken percutaneously (100 samples), under laparoscopic control (53 samples) or post mortem (14 samples) before, during and up to 200 days after the controlled copper intake. Analysis of copper concentration in the liver tissue was done by a modified photometrical Bathocuproin-method after cold extraction with hydrochloric and trichloracetic acid. By using a parallel specimen blank with added EDTA, disturbing factors of the sample matrix were eliminated. The method was evaluated by the atom-absorption-spectroscopy after wet incineration as well as by standard addition of copper titrisol. The correlation with the reference method was very good (r > 0.99); the recovery rate after standard addition was 95 +/- 5.4%. The maximum copper concentrations in the liver were reached after the completion of the copper dosage. Blackheaded sheep showed significantly higher values (480 +/- 173 mg/kg wet tissue weight) than Merino sheep (338 +/- 103). The values of the control animals were 36 +/- 18 mg/kg. In the copper dosed rams the course of copper storage in the liver tissue could be described by an multiple regression with an accuracy of r2 > 0.75. The half-life of the copper concentration in the liver after exceeding maximum levels was 175 +/- 91 days. The pathogenetic role of the copper retention in the dosed animals was proven by regularly increased values of the hepatocellular enzyme glutamate dehydrogenase in the plasma.