Turnover and excretion of copper in rats as measured with 67Cu

We have examined the whole-body turnover and excretion of copper in rats, using 67Cu. Female Fischer rats, 3-4 mo of age, were injected intraperitoneally with tracer doses of 67CuCl2, and whole-body radioactivity was monitored over the next 3-6 days. The rate of loss was exponential and biphasic, with a half-life of 67 h for the first 70 h, followed by a much slower rate over the following days. A small percentage (2-7%) of the early loss was in the urine, the rest in the feces. In sexually immature animals, turnover was slower in the first and faster in the second phases. Pretreatment of rats with a large dose of copper had no significant effect on the initial turnover rate. Ligation of the common bile duct cut the rate in half, but did not block turnover. It is concluded that there are at least two pools of copper in the rat that turn over at different rates and that excretion of copper occurs via the bile and also by other intestinal routes.