Copper in serum

J. "Determination of Copper In Serum With a Graphite Rod Atomizer for Atomic Absorption Spectrophotometry". Anal. Chlm. Acta (1971), 263-269. 

In rodents, copper administered by single intraperitoneal or subcutaneous injection is lethal at 3 to 7 mg Cu/kg BW (Table 3.7). Mice died when their drinking water contained 640 mg Cu/L (Table 3.7). In rats, copper accumulation in kidneys and lungs is similar regardless of route of administration (Romeu-Moreno et al. 1994). Concentrations of copper in serum of rats (Rattus sp.) reflect dietary copper concentrations in liver and kidney are directly related to serum Cu and ceruloplasmin (Petering et al. 1977). As serum Cu concentrations rise in rats, levels fall for serum cholesterol, triglycerides, and phospholipids (Petering et al. 1977). 

Colorimetric Assay for Copper in Serum Standard Copper Solutions. Dissolve l.OOOg of copper foil in die minimum volume of a 50% solution of nitric acid, and add sufficient of a 1% solution of nitric acid to produce 1000 ml. This solution contains 1 mg of Cu in 1 ml. Serially dilute the solution with water to produce solutions containing 0.5, 1.0, 1.5, and 2.0 jag of Cu in 1 ml. 

Copper and Certdoplasmin in the Newborn and in Children. Tissue copper concentrations at birth are relatively high, particularly in the liver. However, concentration of copper in serum is lower at birth than at any other time. It is particularly high in the mother, approximately five times as much as that of the newborn (118). It is believed that the difference between the mother and the baby is attributable to the diminished capacity of the newborn to synthesize ceruloplasmin (16). Since unbound copper can pass the placental barrier, its concentration is the same on both sides of the placenta, but this is not the case with the protein-bound copper ceruloplasmin, which constitutes the majority of copper in serum. 

Abe A, Yamashita S, Noma A. Sensitive, direct colorimetric assay for copper in serum. Clin Chem 1989 35 552-4. 

Menkes syndrome (Menkes steely-hair syndrome) is a rare, X-linked recessive disorder in which infants have low levels of copper in serum and in most tissues except kidney and intestine, where the concentration is very high. They also have greatly reduced plasma ceruloplasmin levels. Hair of the affected infants has a characteristic color and texture (pili torti, twisted hair ). It appears tangled and dull, has an ivory or grayish color, and is friable. Weakness and depigmentation of hair and defects in arterial walls (leading to aneurysms) are explained by loss of activity of copper-dependent enzymes (Table 37-5). Cerebral dysfunction may be due to a disturbance in energy metabolism or neurotransmitter synthesis secondary to decreased activity of cytochrome oxidase and dopamine... 

Copper in serum and natural waters was determined with bathocuproinedisulfonic acid using bromophenol blue as internal standard [8]. Extraction (CHCI3) with Aliquat 336 preceded the spectrophotometric measurement. The ratio of the absorbances at 471 nm (copper complex) and 602 nm (internal standard) was taken as the analytical parameter. Detection limit was 0.4 g f. ... 

Johnson (J3) has reported a relatively simple method for determining copper in serum by electrometric titration. 

A small but important fraction of serum copper is not bound to ceruloplasmin. Most of this non-ceruloplasmin-bound copper is attached to serum albumin. The amount of this fraction of serum copper varies in physiological and especially in pathological conditions. It can be measured since it will react with diethyldithiocarbamate directly, whereas ceruloplasmin-bound copper will react only after acidification. A method for the determination of direct reacting copper in serum has been published by Gubler et al. (G12). Unfortunately, this method is not very accurate, especially in the case of normal subjects where the figures are very low. More exact measurements can be obtained when the values are higher as in certain pathological states. 

Alternatively, the sample can be inserted twice and only one of the established zones merges with the specific reagent used for discriminating purposes, as demonstrated by the spectrophotometric determination of zinc and copper in serum [21],... 

M. Tachibana, T. Imamura, M. Saito, and K. Kina, Rapid Determination of Copper in Serum by Flow Injection Analysis with Water Soluble Azo Dye [in Japanese]. Bunseki Kagaku, 32 (1983) 776. 

Fig. 1. Precision of the determination of copper in serum as a function of the concentration.

The German "Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area, Working Group Analytical Chemistry" has developed a continuous nebulization FAAS method for copper in serum based on a 1 -r- 1 dilution (dilution depends on the applied burner system) with a determination limit of 0.1 mg/L At a mean copper concentration of 1.24 mg/L the within batch precision was 2.4% and the day-to-day precision 3.2% (Winter and Schaller, 1985). Accuracy was checked against certified reference materials. The method was applied on fortified samples from a serum pool of healthy persons and compared by a GF/ AS method developed and tested at the same time (Angerer et al., 1985). The FAAS method is still in successful routine use in a number of German laboratories because of its reliability, simplicity and speed (Schaller, 1993). 

Manning (1975) was the first to exploit the observations that small sample volumes (100 nL) could be used for peak absorption measurements by FAAS with negligible loss in sensitivity. He applied this to the determination of copper in serum by injecting 100 sample volumes into PTFE cone coupled directly to the capillary of a nebulizer burner and obtained an RSD of 3% at 15.7 nebulizer capillary and calibration is difficult. 

Angerer et al. (1985) developed a GFAAS method for the determination of copper in serum and urine. The samples were directly injected into the graphite tube. The injected volume was 10 for serum and 50 /matrix matched samples. Within run precision for serum with 1 mg/L copper concentration was 2.3%, for urine in the range of 20.8 to 126.6 g/L from 2.3% to 4.1%. Accuracy was tested with reference samples and by the FAAS method developed at the same time (Winter and Schaller, 1985). Under the given conditions the detection limit was 0.015 mg/L for serum and 3 Wg/L for urine. 

In general, serum copper values parallel those of ceruloplasmin. Therefore, serum copper is frequently low in patients with Wilson disease. However, about half of patients have serum copper levels in the normal range. Patients with fulminant Wilson disease and/or hemolytic anemia may even have markedly increased levels. Most of the copper in serum is bound to ceruloplasmin, and nnder normal conditions, less than 5% circulates as free copper and does not exceed 10 pg dl in normal subjects. The free copper concentration can be calculated by subtracting from the total copper concentration the ceruloplasmin bound copper (ceruloplasmin times 3.3). 

If a decoppering agent is used for treatment, the compliance can be tested by repeated measurements of the 24 h urinary copper excretion. This approach is not useful if patients are treated with zinc. The dose of d-penicillamine can be lowered if in a compliant patient urinary copper excretion decreases over time and stabilizes at < 500 p g/day. Efficacy of treatment can be monitored by the determination of free copper in serum, and depending on the presenting symptoms. Liver disease can be assessed by routine liver function tests. Repeated liver biopsies with measurement of hepatic copper content are not helpful. Improvement of neurological symptoms can be documented by clinical examination or by auditory evoked brainstem potentials. In addition, some of the MRI abnormalities are fully reversible on treatment. 

A recent sensitive direct procedure for simultaneously measuring iron and copper in serum has been described [59]. This assay utilizes nitro-PAPS, 2-(5-nitro-2-pyridylazo)-5-(V-propyl-A/-sui-fopropylamino)phenol, as the chromogenic metal chelator, and thioglycolate to quantitate interference from copper. The chelator is water-soluble and is 4.5 times more sensitive than bathophen-anthroline for iron. Hemoglobin and lipid produced positive biases in this direct serum procedure. 

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