PHOTOMETRICAL DETERMINATION OF COPPER CON CENTRATION IN THE LIVER DURING EXPERIMENTAL CHRONIC COPPER POISONING OF SHEEP

15 castrated rams were exposed to an oral copper-dosage of 3.64 mg/d/k g 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 t he controlled copper intake. Analysis of copper concentration in the l iver tissue was done by a modified photometrical Bathocuproin-method a fter cold extraction with hydrochloric and trichloracetic acid. By usi ng a parallel specimen blank with added EDTA, disturbing factors of th e 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 w as 95+/-5.4%. The maximum copper concentrations in the liver were reac hed after the completion of the copper dosage. Blackheaded sheep showe d significantly higher Values (480+/-173 mg/kg wet tissue weight) than Merino sheep (338+/-103). The values of the control animals were 36+1 8 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 accu racy of r(2) > 0.75. The half-life of the copper concentration in the liver after exceeding maximum levels was 175+/-91 days. The pathogenet ic role of the copper retention in the dosed animals was proven by reg ularly increased values of the hepatocellular enzyme glutamate dehydro genase in the plasma.