Abstract:We investigated the role of metallothionein (MT) in tissues after cessation of cadmium (Cd) exposure. Wistar rats of both genders were given CdCl 2 in drinking water at daily doses of 0, 2.5, 5.0 or 10.0 mg Cd ⁄ kg body-weight for 12 weeks. Half of the animals were then killed; the others were given Cd-free water for the following 16 weeks, i.e. until 28 weeks after start of the experiment (28-week rats). We observed dose-dependent increases in the levels of MT in the tissues of rats 12 weeks after beginning the experiment (12-week rats). After the exposure ceased, levels of MT in the 28-week rats changed in three ways: an increase in the liver, persistence in the kidney cortex and a decrease in the medulla, relative to those levels in their 12-week counterparts. Biomarkers of kidney dysfunction were determined to be urinary MT (UMT) and urinary N-acetyl-b-D-glucosaminidase (UNAG). After 12 weeks, we observed dose-related statistically significant increases in UMT and UNAG in all of the Cd-exposed groups. A statistically significant decrease for UNAG between the 12-and 28-week rats occurred among males at the lowest Cd dose and for UMT in all of the Cd-exposed groups. The unchanged tissue levels of MT in the kidney cortex suggest that decreased UMT is a sign either of (i) decreased transport of Cd-MT from the liver via blood plasma to the renal tubules or (ii) increased tubular reabsorption and recovery of renal tubular function.Occupational or environmental exposure to cadmium (Cd) can give rise to adverse health effects, particularly kidney damage, as a result of Cd accumulation in the kidneys [1][2][3]. Exposure through inhalation or food intake can lead to acute or chronic effects in humans. There is an important ongoing discussion in the scientific literature regarding the possible reversibility of mild and early forms of Cd-induced renal dysfunction. Human evidence, however, remains inconsistent: some authors [4][5][6] have observed that less severe renal tubular damage is reversible; others [7][8][9] have reported that, according to their experience, progression is the rule. In addition, there is only limited data available from animal experiments involving long-term oral exposure [10,11].Metallothioneins (MTs) have attracted much attention in studies of Cd toxicity since their isolation from the equine renal cortex more than 50 years ago (reviewed by Nordberg [12]). MTs comprise a family of low molecular mass (6-7 kDa) stress proteins incorporating a high content of cysteine and divalent metals. They are important participants in the homeostasis of essential trace elements (e.g. zinc, copper) and function as scavengers of free radicals. Some of the present authors [1,13] were among the first to describe the role of MTs in relation to the toxicology of Cd (reviewed by Nordberg [12]). MTs are important agents for the absorption, transport, and excretion of Cd [1,[14][15][16][17]. Studies of Cd-exposed MT knockout mice [18,19] and in a human population [20] have further underlined the significance ...

Detection of Mutant p53 Protein inWorkers Occupationally Exposed to Benzidine: Cui-Qin XIANG, et al. Shanghai Municipal Center for Disease Control & Prevention, China-To investigate the expression of mutant p53 protein in workers occupationally exposed to benzidine, we detected mutant p53 protein by immuno-PCR assay in the serum of 331 benzidine-exposed healthy workers, while we classified exfoliated urothelial cells in urine samples with Papanicoloau's grading (PG). The Papanicoloau's grading classified exfoliated urothelial cells of the subjects from grade I (normal cells) to grade III (suspicious malignant cells). The subjects were also divided into high, medium and low exposure groups according to the exposure intensity index. The results revealed that mutant p53 protein in the medium and high exposure groups were significantly higher than the in low exposure group (p<0.05), and in PG II and III were significantly higher than in the PG I (p<0.05). There was no significant differences among Papanicoloau's gradings strata in the low exposure group on the incidence and quantity of mutant p53 protein. In the medium and high exposure groups, the incidence and/or quantity of mutant p53 protein in the stratum of PG II and/or III were significantly higher than that of PG I (p<0.05). Detection of mutant p53 protein in conjunction with benzidine exposure level and Papanicoloau's gradings of exfoliated urothelial cells could provide more information to help us elevate surveillance efficiency and diagnose bladder cancer in the early period. (J Occup Health 2007; 49: 279-284)