Copper is an essential nutrient to all higher plants and animals. Physiologically, it exists as an ion in the body. In animals, it is found primarily in the bloodstream, as a cofactor in various enzymes, and in copper-based pigments. In the body, copper shifts between the cuprous (Cu1+) and cupric (Cu2+) forms, though the majority of the body's copper is in the Cu2+ form. The ability of copper to easily accept and donate electrons explains its important role in oxidation-reduction (redox) reactions and in scavenging free radicals. Copper is a critical functional component of a number of essential enzymes known as cuproenzymes. For instance, the copper-dependent enzyme, cytochrome c oxidase, plays a critical role in cellular energy production. By catalyzing the reduction of molecular oxygen (O2) to water (H2O), cytochrome c oxidase generates an electrical gradient used by the mitochondria to create the vital energy-storing molecule, ATP. Another cuproenzyme, lysyl oxidase, is required for the cross-linking of collagen and elastin, which are essential for the formation of strong and flexible connective tissue. Another cuproeznyme, Monoamine oxidase (MAO), plays a role in the metabolism of the neurotransmitters norepinephrine, epinephrine, and dopamine. MAO also functions in the degradation of the neurotransmitter serotonin, which is the basis for the use of MAO inhibitors as antidepressants. One of the most important cuproenzymes is Superoxide dismutase (SOD). SOD functions as an antioxidant by catalyzing the conversion of superoxide radicals (free radicals or ROS) to hydrogen peroxide, which can subsequently be reduced to water by other antioxidant enzymes. Two forms of SOD contain copper: 1) copper/zinc SOD is found within most cells of the body, including red blood cells, and 2) extracellular SOD is a copper-containing enzyme found at high levels in the lungs and low levels in blood plasma. In sufficient amounts, copper can be poisonous or even fatal to organisms. Copper is normally bound to cuproenzymes (such as SOD, MOA) and is thus only toxic when unsequestered and unmediated. It is believed that zinc and copper compete for absorption in the digestive tract so that a diet that is excessive in one of these minerals may result in a deficiency in the other. An imbalance of zinc and copper status might be involved in human hypertension.
belongs to the class of inorganic compounds known as homogeneous transition metal compounds. These are inorganic compounds containing only metal atoms,with the largest atom being a transition metal atom.
Excess copper is sequestered within hepatocyte lysosomes, where it is complexed with metallothionein. Copper hepatotoxicity is believed to occur when the lysosomes become saturated and copper accumulates in the nucleus, causing nuclear damage. This damage is possibly a result of oxidative damage, including lipid peroxidation. Copper inhibits the sulfhydryl group enzymes such as glucose-6-phosphate 1-dehydrogenase, glutathione reductase, and paraoxonases, which protect the cell from free oxygen radicals. It also influences gene expression and is a co-factor for oxidative enzymes such as cytochrome C oxidase and lysyl oxidase. In addition, the oxidative stress induced by copper is thought to activate acid sphingomyelinase, which lead to the production of ceramide, an apoptotic signal, as well as cause hemolytic anemia. Copper-induced emesis results from stimulation of the vagus nerve. (24, 30, 1, 27)
Metabolism
Copper is mainly absorbed through the gastrointestinal tract, but it can also be inhalated and absorbed dermally. It passes through the basolateral membrane, possibly via regulatory copper transporters, and is transported to the liver and kidney bound to serum albumin. The liver is the critical organ for copper homeostasis. In the liver and other tissues, copper is stored bound to metallothionein, amino acids, and in association with copper-dependent enzymes, then partitioned for excretion through the bile or incorporation into intra- and extracellular proteins. The transport of copper to the peripheral tissues is accomplished through the plasma attached to serum albumin, ceruloplasmin or low-molecular-weight complexes. Copper may induce the production of metallothionein and ceruloplasmin. The membrane-bound copper transporting adenosine triphosphatase (Cu-ATPase) transports copper ions into and out of cells. Physiologically normal levels of copper in the body are held constant by alterations in the rate and amount of copper absorption, compartmental distribution, and excretion. (24, 26)
No indication of carcinogenicity to humans (not listed by IARC).
Uses/Sources
Copper is used as a thermal conductor, an electrical conductor, a building material, and a constituent of various metal alloys such as brass and bronze. Copper compounds have been widely used historically as pigments in decorative art. Copper compounds are also commonly used in agriculture to treat plant diseases like mildew, for water treatment, and as preservatives for wood, leather, and fabrics. (24, 25)
Copper toxicity, also called copperiedus, refers to the consequences of an excess of copper in the body. Copperiedus can occur from eating acid foods cooked in uncoated copper cookware, or from exposure to excess copper in drinking water or other environmental sources. Very-high doses of copper can damage liver and kidneys, and can even cause death. Copper may induce allergic responses in sensitive individuals. (25, 26)
Symptoms
Breathing high levels of copper can cause irritation of the nose and throat. Acute symptoms of copper poisoning by ingestion include vomiting, hematemesis (vomiting of blood), hypotension (low blood pressure), melena (black "tarry" feces), coma, jaundice (yellowish pigmentation of the skin), and gastrointestinal distress. Individuals with glucose-6-phosphate deficiency may be at increased risk of hematologic effects of copper. Hemolytic anemia resulting from the treatment of burns with copper compounds is infrequent. Chronic (long-term) effects of copper exposure can damage the liver and kidneys.
Treatment
In cases of suspected copper poisoning, penicillamine is the drug of choice, and dimercaprol, a heavy metal chelating agent, is often administered. Vinegar is not recommended, as it assists in solubilizing insoluble copper salts.
