Retention in the body

A summary of the properties of the different types of dextrans available is presented in Table 25.1. Dextrans for clinical use as plasma expanders must have moleeular weights between 40000 (= 220 glucose units) and 300000. Polymers below the minimum are excreted too rapidly fiom the kidneys, whilst those above the maximum are potentially dangerous because of retention in the body. In practice, infusions containing dextrans of average molecular weights of40000,70000 and 110000 are commonly encountered. 

Nickel retention in the body of mammals is low. The half-time residence of soluble forms of nickel is several days, with little evidence for tissue accumulation except in the lung (USEPA 1980, 1986). Radionickel-63 (63Ni) injected into rats and rabbits cleared rapidly most (75%) of the injected dose was excreted within 24 to 72 h (USEPA 1980). Nickel clears at different rates from various tissues. In mammals, clearance was fastest from serum, followed by kidney, muscle, stomach, and uterus relatively slow clearance was evident in skin, brain, and especially lung (Kasprzak 1987). The half-time persistence in human lung for insoluble forms of nickel is 330 days (Sevin 1980). 

The adrenal glands secrete over 50 different steroids, the most important of which are aldosterone and hydrocortisone. Aldosterone causes salt retention in the body. It is not commercially available. Hydrocortisone is useful for its anti-inflammatory and antiallergic activity. Cortisone and its derivatives have similar activity and it is reduced in vivo to hydrocortisone. The two substances are used to treat rheumatoid arthritis. The 11-P-hydroxyl of hydrocortisone is believed to be of major importance in binding to the receptors of enzymes. Anti-inflammatory activity is significantly Increased by various substituents 6a-fluoro, 9a-fluoro, 21-hydroxy, 2a-methyl, 9a-chloro, and a double bond at C-1. 

Corticosteroids potentially used in food-producing animals include a variety of compounds such as cortisone, cortisol, prednisone, prednisolone, methylpredniso-lone, betamethasone, dexamethasone, flumethasone, fluoroprednisolone, isoflu-predone, and triamcinolone. Corticosteroid administration to feedlots as growth-promoting agents has been recently introduced illicitly in animal production because of their ability to promote water retention in the body. This use has been strongly enhanced for commercial reasons, in order to produce meat more appealing to consumers, due to the juicy and lean look. It is therefore crucial to rely on accurate, sensitive and specific analytical methods to measure residues in biological samples. 

Ahmed et al. (1982) examined the distribution of [l- Cjacrylonitrile (46.5 mg/kg bw orally) in rats. Some 55% of the dose was recovered in the excreta in 24 h (urine, 40% faeces, 2% exhaled as CO . 9% as H (. 0.5% and acrylonitrile, 4.8%). In addition to appreciable retention in the erythrocytes (a feature of the behaviour of meta-bolically formed thiocyanate noted by Bollard et al., 1997), there occurred covalent binding to tissue macromolecules in liver, kidney, spleen, brain, limg and heart. Ahmed et al. (1983) also compared the tissue distribution of [l- C]- and 2,3- - C]aciylonitrile in rats at the same dose level (46.5 mg/kg bw). There was much more covalent binding of radioactive species in all organs examined after administration of [2,3- - C]acr lo-nitrile, suggesting that metabolites other than thiocyanate play a major role in its retention in the body. 

Zenda T, Murase Y, Yoshida I, Muramoto H, Okada T, Yagi K. Does the use of insulin in a patient with liver dysfunction increase water retention in the body, i.e. cause insulin oedema Em J Gastroenterol Hepatol 2003 15 545-9. 

Several animal studies have examined potential age-related differences in the distribution, neurotoxicity, skeletal toxicity, and interactions of aluminum. However, conflicting results have been found and the database is not adequate to assess whether these differences are due to the animal species tested, the aluminum compound used, or the route of exposure. Additionally, there are no studies on the influence of immature renal function on aluminum retention in the body and no studies on the long-term effects of aluminum exposure on skeletal maturation or neurotoxicity. Multiple species studies examining a wide range of effects in immature, mature, and older animals would be useful in assessing the children s susceptibility to the toxicity of aluminum. 

Antidiuretic hormone (ADH) a hormone which is responsible for the regulation of water retention in the body. It is also called arginine vasopressin (AVP) or argipressin. 

SODIUM The most abundant extracellular cation (positive ion). It influences the degree of water retention in the body and is an important participani in the control of acid-base balance. 

In a study with rats, the maximal uptake of various zirconium compounds from the gastrointestinal tract was found to be 0.2% of the elemental zirconium dose (Fletcher 1969). In another study, an uptake of only 0.001% of a zirconium dose (ZrCl4) from the gastrointestinal tract into the bloodstream was demonstrated (Clayton and Clayton 1981). In suckling rats, the levels of absorption were higher and resulted in 10- to 1000-fold higher levels of retention in the body (Shiraishi and Ichikawa 1972, DFG 1998). 

Diuretic, Antidiuretic and Local Anesthetic Agents. Aldosterone, a natural hormone of the adrenal cortex promotes retention in the body of sodium and water, and facilitates excretion of potassium. Hence its effect is almost diametrically opposed to diuretics—especially the thiazide diuretics. Aldosterone is much more active in this respect than desoxycorticosterone. and is used in the treatment of Addison s disease, a hypofunction of the adrenal glands. 

Its meehanism of action is almost similar to that of chlorothiazide (CTZ) in the relief of fluid retention in the body. 

In this regard, the pituitary hormone vasopressin helps water retention in the body by its reabsorption in the renal tubules and thus controls expression of the gene hyaluronan synthase-2 in the kidney [46]. 

The recommended daily dietary doses of copper are 0.4-0.7 mg for children under 1 year, 0.7-2.0 mg for children aged 1 to 10 years, 1.5-2.5 mg for adolescents and 1.5-3.0 mg for adults. Resorption of copper and its retention in the body depend on the chemical form in which this element is present in the diet. Experiments on laboratory animals have shown a higher utilisation of copper in the form of neutral and anionic complexes contained in plant material than in the form of copper sulfate. Availability of copper increases the presence of proteins and amino acids in the diet. Also, carboxylic and hydroxycarboxylic acids stimulate resorption of copper. In contrast, higher doses of ascorbic acid, fructose, molybdenum, sulfur compounds and zinc significantly reduce the resorption of copper. Ascorbic acid reduces cupric compounds to slightly soluble cuprous compounds. The effect of phytic acid and dietary fibre on copper resorption is, in comparison with the effect of these components in zinc, less pronounced. 

When the sampling period does not enable the biological half-life of the radionuclide to be estimated, assuming a long period of retention in the body for the purpose of dose assessment may result iu an underestimate of the intake, and hence of the committed effective dose. The degree of over- or under-estimation of the dose will depend upon the overall pattern of retention in the body. 

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