Absorption, transport and distribution of copper.

This paper deals with the way animals regulate the supply of copper to sites within the body where the metal exercises its functions. Homeostasis is maintained by the control of both absorption and excretion of the metal, although the efficiency with which this balanced is achieved varies between species. These processes are influenced by dietary intake of copper and they also depend on genetic factors, age, dietary composition and the physiological state of the animal. Some of these effects are described, with emphasis on the possible mechanism of absorption of the metal. The distribution of copper after its absorption from the intestine and, in particular, its uptake by the liver and kidneys are also discussed. Much of the copper removed by these organs is incorporated into, and may induce synthesis of, metallothionein. The precise role of this protein in copper metabolism is still, however, a matter of conjecture. The subsequent binding of hepatic copper to metalloenzymes, its excretion in bile and its incorporation into lysosomes during copper overload are also considered.