Clinical aspects of selenium metabolism

Histopathological and biochemical alternations of the heart induced by acute cadmium exposure in the freshwater crab Sinopotamon yangtsekiense

Cadmium (Cd) is a highly toxic element in water. Its toxicity has been attributed to oxidative stress mediated by free radicals. Here we investigated the effects of Cd on the histopathology, antioxidant enzymes and lipid peroxidation of crustacean heart. The freshwater crabs Sinopotamon yangtsekiense were exposed to different concentrations of Cd for 1, 3, 5 and 7d. After exposure, histological abnormalities were discovered, including myocardial edema, vacuolar and vitreous degeneration, and infiltration of inflammatory cells. Additionally, alterations in nuclei, mitochondria, rough endoplasmic reticulum as well as myofibrils were observed. Meanwhile, superoxide dismutase (SOD) activity was significantly increased after Cd exposure. Catalase (CAT) activity was only increased in the group exposed to 14.50 mg L(-1) Cd on day 5 and decreased with increasing Cd concentration and exposure time. Glutathione peroxidase (GPx) activity was increased in groups treated with 29.00, 58.00 and 116.00 mg L(-1) on days 1 and 3, and decreased thereafter. Besides, malondialdehyde (MDA) levels were significantly increased after 3d of Cd exposure at all the indicated concentrations. These results showed that acute Cd exposure led to harmful effects on the histology of crab heart, which are most likely linked to Cd-induced oxidative stress.

Acute effect of cadmium treatment on the kidney of rats: biochemical and ultrastructural studies

The present study was designed to explore the nephrotoxic effect of intraperitoneal acute administration of CdCl2 (2.5 and 5 mg kg(-1) b.w.) in rats. A number of toxicological parameters in kidney were examined including malondialdehyde (MDA) and endogenous antioxidants, e.g., catalase (CAT), superoxide dismutase (SOD) and Glutathione Peroxidase (GPx). The parameters that indicate tissue damage such as serum urea and creatinine were also determined, along with the ultrastructural changes of kidneys. A correlation was found between the dose and the intensity of changes. The results demonstrated that cadmium administration increased renal MDA but decreased CAT, SOD and GPx activities. In parallel, serum creatinine and urea elevated. The glomerular ultrastructural changes observed in cadmium-treated rats included narrowing of the capillary lumen and swelling of the capillary endothelium with occasional loss of fenestrae. The mesangium was wide with increased mesangial matrix. Loss of homogenous appearance of basement membrane displaying ondulation and thickening in many areas and deterioration of the slit membrane structures formed by the podocytes were also noted. The effects of cadmium on proximal cell ultrastructure were focal loss of brush border, nuclear membrane damage, chromatin condensation, swelling of the mitochondria with regression of mitochondrial cristae, degranulation and disintegration of protein-synthesizing structures such as rough endoplasmic reticulum, increased number of lysosomes and ultimately cell death.

Direct determination of selenium in human blood plasma and seminal plasma by graphite furnace atomic absorption spectrophotometry and clinical application

Direct determination of selenium (Se) in body fluids by graphite furnace atomic absorption spectrophotometry (GFAAS) may suffer from problems like severe background, matrix effects, preatomization losses, and spectral interferences. In this study we evaluate critically the influence on the accuracy of the direct determination of Se in blood plasma and seminal plasma by GFAAS, and propose a simple, rapid, and accurate method, suitable for routine clinical analysis. The method for blood plasma is mainly based on studies by the use of matched matrix and a Pd-Ni modifier, but for seminal plasma only a Pd modifier is required. The method developed was also applied to study the Se distribution in plasma protein fractions of patients with hepatocellular carcinoma. The Se in plasma of patients was significantly lower than that of the controls. The distribution pattern of Se in blood plasma fractions of patients was also different from that of the controls.

Defence mechanisms against free radical-induced damage in sheep, cattle and dog erythrocytes

1. Erythrocytes from sheep were to be found the least resistant to peroxidative stress induced in vitro as compared to those from cattle and dogs. 2. The differences found among species in alpha-tocopherol content and glutathione peroxidase activity were probably insufficient to explain the lowest resistance. 3. One of the main reasons of the lowest resistance may be found in the membrane composition and characteristics (membrane fluidity).

Selenium--its biological perspectives

Selenium is an essential trace element at lower concentrations and toxic at higher concentration. Animals can metabolize both inorganic and organic forms and convert non methylated Se to mono--or di--or tri--methylated forms, of which, mono-methylated forms are most toxic. Glutathione reductase converts selenoglutathione to H2S in liver and erythrocytes and is ultimately excreted. Se effects the toxicities of xenobiotic agents, provides antagonistic effect to Sulphur and co-administration with Zn increase Se retention in certain organs. At its toxic level (4-8 ppm) it increases Cu contents of heart, liver and kidney and has detoxifying or protecting effect against Cd and Hg. It is a prosthetic group of several seleno metalloenzymes. The concentration of the element is decreased in serum/plasma or erythrocytes of patients of AIDS, trisomy-21, Crohn's and Down's syndrome, phenylketonurea, Keshan's disease and cancer. Rather, the element has antiproliferative and cancer protecting effect. Se content of testes increases considerably during pubertal maturation and, during Se deficiency, the supply to the testes has priority over the other tissues. The element is localized in the mitochondrial capsule protein (MCP) and is involved in biosynthesis of testosterone. Neither the age of mother nor the concentration of Se during pregnancy has any effect on weight of baby or the length of pregnancy. Se levels in human milk is affected by maternal intake and its requirements by infants and young children are higher for their rapid growth. Clinical symptoms of its toxicity include severe irritations of respiratory system, metallic taste in mouth, formication of nose, signs of rhinitis, lung edema and brancho-pneumonia. The typical garlic odour of breath and sweat is due to dimethyl-selenide.

Selenium and Behçet's disease

Behçet's disease is an inflammatory disorder of unknown etiology, characterized by recurrent oral and genital aphthous ulcers, ocular inflammation, and skin lesions of erythema nodosum and acneiform eruptions. Selenium (Se) affects all components of the immune system, i.e., the development and expression of nonspecific, humoral, and cell-mediated responses. In general, a deficiency in Se appears to result in immunosuppression, whereas supplementation with low doses of Se appears to result in augmentation and/or restoration of immunologic functions. In this study, the distribution of Se and IgG, IgM in serum were compared in samples from healthy adult control and Behçet's disease patients. The serum Se levels were measured by AA-30-40 Varian Spectra, and immunoglobulins were measured by immunodiffusion technique. The mean (SD) serum Se level of 54.24 +/- 8.06 ng/mL among Behçet's disease subjects was significantly different (P less than 0.01) from that in the control subjects (90.01 +/- 9.94 ng/mL). We also measured IgG and IgM as 10.01 +/- 2.74 mg/mL and 1.26 +/- 0.29 mg/mL, respectively for patients, and 15.08 +/- 4.73 mg/mL and 1.58 +/- 0.43 mg/mL for controls. The mean values of IgG and IgM for patients were significantly (P less than 0.05) different from the values of controls. It seems, therefore, that a deficiency in selenium impedes the humoral immune response.