Following ingestion of copper, copper levels in the blood rapidly rise. The copper is predominantly
bound to albumin. There is some evidence that albumin plays a passive role in copper transport, carrying
a large portion of the exchangeable copper in the circulation and releasing this to other carriers for actual
cell-specific uptake. There is also evidence that transcuprein is another plasma protein carrier (Weiss and
Linder 1985). Thus, dietary copper is transported to, and enters, the liver and kidney. Copper then
reemerges into the plasma bound to the ceruloplasmin. Ceruloplasmin, which tightly binds six or seven
COPPER 73
3. HEALTH EFFECTS
copper atoms (Musci et al. 1993; Saenko et al. 1994), is the most abundant copper protein in the plasma;
60–95% of the plasma copper is bound to ceruloplasmin (Harris 1993). Copper is transported from the
liver to other tissues via ceruloplasmin. Ceruloplasmin does not enter the cell (Percival and Harris 1990).
Copper, probably as Cu(I) rather than Cu(II) (Dameron and Harris 1989; Percival and Harris 1989), enters
the cell via a carrier-mediated process. The membrane-bound copper transporting adenosine
triphosphatase (Cu-ATPase), which selectively binds copper ions, transports copper ions into and out of
cells (Harris et al. 1998). In most organs and tissues, copper turnover is biphasic (Levenson and
Janghorbani 1994). In the plasma, the half-lives of the first and second components were 2.5 and 69 days,
respectively. It is likely that the first order component is ceruloplasmin associated copper. The respective
calculated copper half-lives for other tissues are 3.9 and 21 days for the liver, 5.4 and 35 days for the
kidney, and 23 and 662 days for the heart; copper turnover in the brain appears to be monophasic with a
half-life of 457 days.