Administration of mannitol with high dose could induce extensive isometric renal proximal tubular vacuolization and acute renal failure in clinic. We previously demonstrated that mannitol-induced human kidney tubular epithelial cell (HK-2) injury. The objective of our present work was to further study the cytotoxicity of mannitol in HK-2 cells and its potential mechanism. Cell viability was assessed by an MTT method. Cell morphological changes were observed. Furthermore, levels of malondialdehyde (MDA) and glutathione (GSH) were measured. Flow cytometry was performed to determine cell apoptosis by using Annexin V-FITC and PI. In addition, the F-actin of cells was labeled by FITC-Phalloidin for observation of cytoskeleton. The MTT assay displayed that the cell viability decreased significantly in a dose- and time-dependent manner. The morphological changes were observed, including cell membrane rapture and cell detachment. The GSH concentration in HK-2 cells decreased dramatically in mannitol treatment group, while MDA content increased significantly. The results of flow cytometry indicated that apoptotic percentages of HK-2 cells increased in 250 mmol/L mannitol treatment group. After treatment with 250 mmol/L mannitol for 48 h, HK-2 cells showed disorganization of cytoskeleton and even exhibited a totally destroyed cytoskeleton. Therefore, high dose of mannitol has a toxic effect on renal tubular epithelial cells, which might be attributed to oxidative stress, destroyed cellular cytoskeleton and subsequent cell apoptosis.

Homocysteine is an amino acid containing a free sulfhydryl group, making it probably contribute to the antioxidative capacity in the body. We recently found that plasma total homocysteine (total-Hcy) concentration increased with time when whole blood samples were kept at room temperature. The present study was to elucidate how increased plasma total-Hcy is produced and explore the potential physiological role of homocysteine. Erythrocytes and leukocytes were separated and incubated in vitro; the amount of total-Hcy released by these two kinds of cells was then determined by HPLC-MS. The effects of homocysteine and methionine on reactive oxygen species (ROS) production, osmotic fragility, and methemoglobin formation in erythrocytes under oxidative stress were studied. The reducing activities of homocysteine and methionine were tested by ferryl hemoglobin (Hb) decay assay. As a result, it was discovered that erythrocytes metabolized methionine to homocysteine, which was then oxidized within the cells and released to the plasma. Homocysteine and its precursor methionine could significantly decrease Rosup-induced ROS production in erythrocytes and inhibit Rosup-induced erythrocyte’s osmotic fragility increase and methemoglobin formation. Homocysteine (but not methionine) was demonstrated to enhance ferryl Hb reduction. In conclusion, erythrocytes metabolize methionine to homocysteine, which contributes to the antioxidative capability under oxidative stress and might be a supplementary protective factor for erythrocytes against ROS damage.

Shantou, a city in the People's Republic of China, has a central urban population of approximately 700,000 and a large number of registered vehicles (motorcycles = 256,600; other motor vehicles = 261,000). Shantou is designated as 1 of the 5 Special Economic Zones in China. The use of leaded gasoline was prohibited in the city at the end of 1998. Blood samples for lead analysis were collected from children aged 1-5 yr during the summers of 1999-2001, and the samples were analyzed using graphite furnace atomic absorption spectrometry. In 1999, 44.3% (147/332) of the children had mean blood lead levels in excess of 100 microg/l. The percentage of children with blood lead levels that exceeded 100 microg/l was reduced to 35.8% (227/635) and 23.0% (105/457) in 2000 and 2001, respectively. Average blood lead levels declined from 104 microg/l, to 94 microg/l, and 79 microg/l during the 3-yr period, respectively; the respective concordant geometric means were 97 microg/l, 85 microg/l, and 71 microg/l. Mean blood lead levels for the children studied decreased significantly (p < 0.05) every year. Among all children tested during the 3-yr period, there were no significant differences by gender and no significant differences between children who were between the ages of 2 and 3 yr; however, those who were 4 yr of age had blood lead levels that were significantly (p < 0.05) higher than levels in those 2 and 3 yr of age.