Zinc in hair

There Is an advantage in using a readily obtained sample of head and/or body hair for trace metal analysis. This is a recognised technique when investigating suspected toxic metal exposure, and has been advocated as an index of nutritional status for the essential trace elements (Valcovic, 1977). 

The hair sample is digested as described above for tissue or food samples, and the zinc content determined by flame AAS. 

A sample of 50-100 mg of head hair is collected from the nape of the neck if possible at a standardised distance from the scalp. An important decision is whether or not to wash the hair sample prior to analysis. This is considered important when external contamination is suspected. Chittleborough (1980) concludes that a no washing policy is best and avoids the risk of accidental contamination. 

The clinical usefulness of the measurement is open to question. McBean et al. (1971) did not find a correlation between plasma/serum Zn concentrations and the amount of Zn in hair samples taken from Iranian children. Hair growth is also affected by the restriction of growth caused by nutritional deficiency and the concentration of zinc may be normal in the hair of children known to be malnourished. Additionally, Chittleborough and Steel (1980) found that facial hair zinc did not vary as dosage with Zn salts was increased. 

A further complication is noted by De Antonio et al. (1982) in that they found no correlation between head hair metal content and that of pubic hair. They concluded that variable exogenous contamination by trace metals of hair samples is a major problem. 

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The concentration of zinc in hair appears to reflect chronic zinc nutriture. Thus if the hair has been growing at a reasonable rate, hair zinc is a useful index of chronic zinc status in the body. Hair zinc, however, does not reflect changes in the status of zinc on an acute basis. Similar remarks apply to zinc in the red cells. Ultimately the response to therapy with zinc is probably the most reliable index for making a diagnosis of zinc-deficient state in man. 

Zinc in Hair. Low hair zinc has been associated with poor growth in children, and has been used as a criterion for initiating supplementation studies, However, variables such as hair growth rate and external contamination from hair dyes and cosmetics can cause inconsistent results. Results from individual patients are difficult to interpret. 

Hambidge KM, Hambidge C, Jacobs M, et al. 1972. Low levels of zinc in hair, anorexia, poor growth and hypogeusia in children. Pediatr Res 6 868-874. 

Provost JJ, Munnis P, Morine GH. 1993. Alternate method for determining zinc in hair. Microchemical Journal 47(1-2) 28-32. 

It is very easy to wash out 5-10% of the zinc in hair. After 21 hr treatment with 1 % concentrated nitric acid 90% of the zinc has been removed [31]. These concentration changes in different media support the hypothesis that an element is bound to human hair in several different ways. 

Dollard, G.J. 1986. Glasshouse experiments on the uptake of foliar applied lead. Environ. Pollut. 40A 109-119. Dom, C.R., P.E. Phillips, J.O. Pierce, and G.R. Chase. 1974. Cadmium, copper, lead and zinc in bovine hair in the lead belt of Missouri. Bull. Environ. Contam. Toxicol. 11 626-630. 

Some of the unusual features of pantothenic acid noted by investigators include (1) it promotes amino add uptake (2) it is potentiated by zinc in preventing graying of hair in rats (3) it promotes resistance to stress of... 

In addition to the classical symptoms of zinc deficiency mentioned above, the following unusual conditions have been reported liver and spleen enlargement, abnormal dark adaptation and abnormalities of taste. Several laboratory procedures for diagnosing zinc deficiency are available. Measurement of zinc levels in plasma is useful in certain cases. Levels of zinc in the red cells and hair may be used for assessment of body zinc status. More accurate and useful parameters are neutrophil zinc determination and quantitative assay of alkaline phosphatase activity in neutrophils. Determination of zinc in 24 h urine may help diagnose deficiency if sickle cell disease, chronic renal disease and liver cirrhosis are ruled out. A metabolic balance study may clearly distinguish zinc-deficient subjects. 

Lin et al (17) observed low concentrations of zinc in serum, hair, and esophageal tissue in patients with other types of cancer or with other diseases (Table I). 

Complexes with the thio-oxamate ligands NH2(CO)CSO and NH2(CS)C02, which bind through O and S, exhibit trigonal bipyramidal geometry around the zinc. The zinc complex of the 0,S-donor ligand 2-pyridinethiolate 1-oxide, known as zinc pyrithione, is a fungicide andbacteriocide much used in hair shampoos. 

Excessive ingestion of alcohol may lead to severe deficiency of zinc. In one case, acquired zinc deficiency attributable to alcohol was characterized by mental disturbances, widespread eczema craquele, hair loss, steatorrhea, and dysproteinemia with edema (33). Therapy with zinc reversed these manifestations. A similar clinical syndrome has been seen among Ugandian blacks addicted to banana gin. 

Femses (babies that have not yet been born) deprived of zinc may grow up to have mental or physical problems. Young children who do not get enough zinc in their diet may experience loss of hair and skin lesions. They may also experience retarded growth called dwarfism. Chemists have now found that zinc plays an essential role in the manufacture of many important chemicals in the human body. 

Hair has been used in the biomonitoring of various elements, for example, arsenic, thallium, and zinc, and has been used in the monitoring of drugs and biological substances. The level of mercury in hair is widely used as a biological indicator for exposure to methyl mercury (MeHg). In addition, hair samples have been utilized to evaluate environmental exposure to pollutants such as lead, and occupational exposures to metals such as nickel and chromium. However, the ATSDR has stated ... 

The first two steps in the synthesis of melanin are catalyzed by tyrosinase, a copper-containing oxidase, which converts tyrosine to dopaquinone. All subsequent reactions presumably occur through nonenzymatic auto-oxidation, in the presence of zinc, with formation of the black to brown pigment eumelanin. The yellow to reddish brown, high-molecular-weight polymer known as pheomelanin and the low-molecular-weight trichromes result from addition of cysteine to dopaquinone and further modification of the products. Pheome-lanins and trichromes are primarily present in hair and feathers. 

Amperometric techniques are very useful for detecting analytes that have been separated by chromatographic means but have no chromophores or other easy means of detection. Adsorptive stripping voltammetry (ASV) can be used for the direct sensitive analysis of metals in many types of sample matrix. For example, ASV has been used to determine cadmium, lead and zinc in urine, copper and bismuth in human hair tin in fruit juice, zinc and copper in fish and lead in gunshot residue. Stripping analysis can also be used for other applications such as determining flavanols in wine °, inorganic compounds such as cyanide and pharmaceuticals. ... 

Additional zinc is lost daily in seminal emissions, menstrual losses and hair and naU growth. Semen is rich in zinc and can represent a significant source of zinc loss with frequent ejaculations (one ejaculation contains -9 rmol zinc). Typical hair and nail growth account for only 0.5 jmol zinc loss each day (Baer and King 1984). 

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