钙和镉对金属硫蛋白在小鼠肝合成中的影响

研究了小鼠经口给于钙盐和镉盐后，钙和镉在小鼠肝金属硫蛋白合成中的相互影响。结果发现：单独给于钢（８ｍｇ／ｋｇ）时，镉能诱导肝金属硫蛋白的合成；单独给于钙（２０ｍｇ／ｋｇ）时，肝ＭＴ的含量无明显的增加；但同时经口给于钙和镉（２０＋８ｍｇ／ｋｇ），则肝ＭＴ含量比单独给于镉时的肝ＭＴ含量明显增加（Ｐ＜０．０５），Ｃａ＋Ｃｄ组的肝Ｚｎ浓度大大高于Ｃｄ组。     

半胱氨酸,谷胱甘肽和除去金属的金属硫蛋白对含镉金属…

在大鼠不同部位ＳＣ巯基化合物与含镉金属硫蛋白（ＣｄＭＴ），观察除去金属的金属硫蛋白（ＡｐｏＭＴ）Ｌ－半胱氨酸（Ｃｙｓ），还原型谷胱甘肽（ＧＳＨ）对大鼠ＣｄＭＴ损伤肾的保护作用，测定不同时相尿蛋白和尿碱性磷酸酶活性以及肾组织形态学结果表明，与单独给予ＣｄＭＴ比较，肾损伤作用明显减轻。ＡｐｏＭＴ，ＧＳＨ促使大鼠尿Ｃｄ排泄量显增加，肾组织细胞中金属硫蛋白（ＭＴ）结合Ｃｄ和游离Ｃｄ含量明显降低，以ＧＳＨ     

氯丙嗪、尼莫地平对大鼠体内镉分布的影响

目的　利用亚急性镉 (Ｃｄ)中毒性肾损伤动物模型 ,观察钙调素抑制剂氯丙嗪 (ＣＰＺ)和钙离子通道阻断剂尼莫地平(Ｎｉｍｏ)对体内镉分布的影响。方法　镉组 :腹腔注射Ｃｄ2ｔ1 4ｍｇ ｋｇ(3次 周 ,共 6周 )、ＣＰＺ及Ｎｉｍｏ组染镉 (剂量同镉组 )前分别用ＣＰＺ 4ｍｇ ｋｇ或Ｎｉｍｏ 3ｍｇ ｋｇ预防处理动物。测定血、肝、肾镉含量及肝、肾金属硫蛋白 (ＭＴ)含量。结果　Ｎｉｍｏ组血镉和肝镉含量分别为 0 5 0 5 μｇ ｍｌ和 (4 4 0 7± 7 89)μｇ ｇ肝重 ,均显著低于镉组 (Ｐ <0 5 ) ,肾镉含量与镉组比较 ,差异无显著性 ;肝、肾ＭＴ含…     

半胱氨酸，谷胱甘肽和除去金属的金属硫蛋白对含镉金属硫蛋白肾毒性的保护作用

在大鼠不同部位ｓｃ巯基化合物与含镉金属硫蛋白（ＣｄＭＴ），观察除去金属的金属硫蛋白（ＡｐｏＭＴ），Ｌ－半胱氨酸（Ｃｙｓ），还原型谷胱甘肽（ＧＳＨ）对大鼠ＣｄＭＴ损伤肾的保护作用。测定不同时相尿蛋白和尿碱性磷酸酶活性以及肾组织形态学结果表明，与单独给予ＣｄＭＴ比较，肾损伤作用明显减轻。ＡｐｏＭＴ，ＧＳＨ促使大鼠尿Ｃｄ排泄量显著增加，肾组织细胞中金属硫蛋白（ＭＴ）结合Ｃｄ和游离Ｃｄ含量明显降低，以ＧＳＨ尤为明显Ｃｙｓ能增加Ｃｄ在肾细胞内蓄积，提示在Ｃｄ中毒时，除ＭＴ对肾损伤有保护作用外，也有其它巯基化合物的参与，且作用机理不尽相同     

亚硒酸钠防治镉中毒的分子机理

亚硒酸钠防治镉中毒的分子机理王宗元史德浩卞建春任建新王捍东刘学忠（扬州大学农学院动物医学系，扬州２２５００９）用锌诱导大鼠肝，肾细胞合成金属硫蛋白（ＭＴ），再用１０９Ｃｄ置换ＭＴ等蛋白质上的锌，发现１０９Ｃｄ几乎全部与ＭＴ相结合．如向上述肝，肾胞液中...     

镉化合物对大鼠的脂质过氧化作用

镉是一种常见的重金属毒物 ,也是一种重要的工业毒物和环境污染物 ,可引起肝、肾、肺、骨骼等多种器官的损害 ,其中肝、肾是慢性镉接触的最主要靶器官。近年来 ,脂质过氧化 (ＬＰＯ)作为很多毒物作用机理的研究备受关注 ,对镉引起大鼠肾脏产生ＬＰＯ改变也已有了一些研究。但腹腔注射氯化镉(ＣｄＣ2 )与皮下注射镉金属硫蛋白 (ＣｄＭＴ)后 ,镉在体内的分布有较大的差异 ,故利用同一批大鼠研究给予这两种镉化合物 ,测定镉的ＬＰＯ作用 ,对进一步证实镉是否有ＬＰＯ效应有一定意义。1　材料和方法1 1　实验动物及处理　采用雄性Ｗｉｓｔａｒ大…     

镉中毒肾损害大鼠尿中不同分子量镉,锌结合物的研究

研究结果表明,肾功能受损以前,尿镉仅以小分子结合镉的形式排泄;当肾镉负荷超过其临界浓度并引起肾功能障碍后,尿镉排泄急剧增加,其绝大多数以金属硫蛋白结合镉的形式排泄,同时小分子结合镉也继续增多;随着肾损害的加重,尿中又相继出现中、高分子蛋白质结合镉。但是,尿金属硫蛋白结合镉是肾脏受损后尿镉的主要形式。正常动物尿锌主要以小分子结合锌形式存在,镉性肾损害严重时方有尿锌显著升高,且主要系高分子结合锌排泄增多。     

镉在肝脏和睾丸中的分布及与金属硫蛋白的关系

金属硫蛋白 (ＭＴ)是一种低分子量的金属结合蛋白 ,可诱导ＭＴ的生物合成。进入体内的镉与ＭＴ结合 ,一方面与镉在各组织器官中的分布有关 ,另一方面也可缓解镉的毒性效应。本次研究主要观察镉在肝脏和睾丸中的分布及其与ＭＴ的关系。1　材料与方法1 1　材料　氯化镉 (ＣｄＣｌ2 2 5Ｈ2 Ｏ) ,分析纯 ,天津化学试剂厂生产 ;三羟甲基氨基甲烷 (Ｔｒｉｓ) ,进口分装。1 2　实验动物及处理　健康成年雄性Ｓｐｒａｇｕｅ Ｄａｗｌｅｙ大鼠2 4只 ,体重 2 5 0～ 30 0 ｇ,购于上海动物研究中心。随机分为对照组和染毒组 ,每组 6只。低、中、高剂量…     

非蛋白结合镉对镉性肾损害的影响

镉是常见的环境污染物 ,可通过多种途径进入生物体内。肾脏是镉蓄积和毒作用的主要部位 ,其中主要蓄积在肾皮质 ,约为髓质的 3倍以上[1] 。镉在体内主要以镉金属硫蛋白 (ｃａｄｍｉｕｍｍｅｔａｌｌｏｔｈｉｏｎｅｉｎ ,ＣｄＭＴ)的形式存在[2 ] ,另外镉也可以与小分子物质结合或以游离的形式存在。有研究表明非ＭＴ结合的镉在镉的细胞毒性中较总镉具有更重要的意义 ,与镉的肾脏损害有较为直接的联系[3 ] 。1　材料与方法1 1　实验动物与分组　健康Ｗｉｓｔａｒ大鼠 6 4只 ,体重180～ 2 2 0ｇ ,雌雄各半 ,由中南大学湘雅校区实验动物中心提…     

镉中毒肾损害大鼠尿中金属硫蛋白的变化

用Sephadex G-75凝胶层析技术对亚急性镉中毒肾损害大鼠肝、肾、血、尿中金属硫蛋白(MT)进行了分离测定。结果表明,大鼠接受镉后,其肝、肾、血、尿中MT增多;MT是体内镉的主要存在形式;尿中MT增多是镉中毒肾损害最早出现的变化之一,是肾小管功能障碍的灵敏指标,对反映镉性肾损害有其特异性。     

Induction of metallothionein by cadmium-metallothionein in rat liver: a proposed mechanism.

Distribution of Cd to various organs following iv administration of CdCl2 (3.5 mg Cd/kg) resulted in more than 43% of total tissue Cd accumulating in the liver. In contrast, after CdMT administration (0.5 mg Cd/kg), only 1% of the Cd was found in liver. Rats administered CdCl2 (1.0 mg Cd/kg) had hepatic MT values 30-fold greater than controls and a hepatic Cd concentration of 17 micrograms/g. In comparison, rats treated with CdMT (0.4 mg Cd/kg) had hepatic MT concentrations 7-fold greater than controls and a hepatic Cd concentration of 0.80 micrograms/g. However, when hepatic MT levels were normalized to tissue Cd concentrations, induction of MT by CdMT was 5-fold greater than by CdCl2. Northern and slot-blot analyses of mRNA showed that both CdCl2 and CdMT coordinately increased MT mRNA. These data suggest that both CdMT and CdCl2 increase hepatic MT by similar mechanisms. A dose-response increase in MT produced by CdCl2 indicated a biphasic response, with low doses producing relatively more hepatic MT than higher doses. In addition, the amount of MT produced per unit Cd after CdMT treatment was similar to those observed after low doses of CdCl2 in the dose-response experiment. These data provide strong evidence to support the conclusion that the apparent potency of CdMT observed here and in previous studies is most likely due to the small amount of Cd distributed to the liver, which is relatively more effective in inducing MT than are higher concentrations.     

Exogenous metallothionein and renal toxicity of cadmium and mercury in rats.

The relative tissue distribution and toxicity of cadmium (Cd) and mercury (Hg) in the liver and kidneys of rats when the metals are administered as either inorganic salts or complexed with MT were studied. Male Sprague-Dawley rats were injected (i.v.) with Cd or Hg inorganic salt of chloride or in a complex of MT at a dose of 0.3 mg/kg body weight. The concentration of MT and metals in plasma and urine was monitored for 7 days, at the end of which the rats were killed. Injection of both HgCl2 and Hg-MT induced the synthesis of MT only in the kidney but not in the liver, whereas CdCl2 and Cd-MT injections induced MT synthesis in both liver and kidney, respectively. Plasma MT levels increased 3 days after CdCl2 but not after HgCl2 injection, suggesting that hepatic MT may be an important source of plasma MT under our experimental conditions. Renal toxicity was observed morphologically and by an increase in blood urea nitrogen, plasma creatinine, proteinuria in rats injected with Cd-MT and both forms of Hg. Urinary MT excretion was significantly elevated in Cd-MT injected rats compared with those injected with CdCl2. However, HgCl2 and Hg-MT injected rats showed no significant difference in urinary MT excretion. The magnitude in the renal accumulation of Hg is similar after the administration of Hg-MT or HgCl2, but our findings suggest that the site of epithelial injury may be different. Injury effects of Hg-MT localized mainly in the terminal portions of the proximal convoluted tubule and the initial portions of the proximal straight tubule whereas inorganic Hg caused necrosis in pars recta segments of the proximal tubule.     

Kidney synthesizes less metallothionein than liver in response to cadmium chloride and cadmium-metallothionein

Acute exposure to Cd produces liver injury, whereas chronic exposure results in kidney injury. Tolerance to the hepatotoxicity is observed during chronic exposure to Cd due to the induction of metallothionein (MT). The nephrotoxicity produced by chronic Cd exposure purportedly results from renal uptake of Cd-metallothionein (CdMT) synthesized in liver. The change in target organ from liver to kidney might be due to a lower amount of MT synthesized in the kidney in response to CdMT. Therefore, the purpose of the present study was to quantitate hepatic and renal MT induced by CdCl2 and CdMT. MT levels in mice were quantitated using the Cd-heme assay 24 hr after administration of CdCl2 (0.5-3.0 mg Cd/kg) and CdMT (0.1-0.5 mg Cd/kg). In both liver and kidney, MT reached higher levels following administration of CdCl2 (220 and 60 micrograms/g, respectively) than of CdMT (25 and 35 micrograms/g, respectively), probably because higher dosages of CdCl2 than CdMT are tolerated. CdMT produced 19 and 3 micrograms MT/micrograms Cd in liver and kidney, respectively, while CdCl2 produced 11 and 6 micrograms MT/micrograms Cd, respectively. In conclusion, induction of MT occurs in both the liver and kidney after administration of CdCl2 and CdMT. However, the kidney is less responsive than the liver to the induction of MT by both forms of Cd, which may contribute to making the kidney the target organ of toxicity during chronic Cd exposure.     

Turnover of parenterally administered zinc and cadmium and the redistribution of metallothionein bound zinc in newborn rats

The whole body retention, tissue distribution and protein binding patterns of 65Zn were compared with 109Cd in newborn rats during postnatal development. One-day-old pups received a single injection of either 65Zn (2.5 microCi) or 109Cd (2.5 microCi plus 1 mg Cd/kg as CdCl2). During the 22 days of age, the whole body retention of 109Cd was higher than that for 65Zn. The biological half times were 466 and 46.3 days for 109Cd and 65Zn, respectively. There were marked differences in tissue deposition of these metals. Both liver and kidney accumulated more 109Cd than other tissues while the 65Zn showed a uniform distribution, with a gradual decrease in radioactivity with age. At the time of weaning, 109Cd had accumulated mainly in liver and kidney whereas, 65Zn was found predominantly in bone and skin. The specific binding of 109Cd to hepatic MT in newborn rats did not change with growth. Although a significant amount of 65Zn initially accumulated in the MT fractions in the liver, it was transferred gradually to high molecular weight protein fractions during development. The administration of these 2 metals had no effect on the body weight, liver weight and total hepatic zinc concentration. However, a significantly high content of MT and zinc in MT fractions was detected in the livers of Cd-treated rats at 22 days of age. The results show the transfer of the essential metal, zinc from hepatic MT to other proteins and the specific binding of cadmium, the non-essential metal to MT during postnatal development in rats.     

Induction of metallothionein synthesis by zinc in cadmium pretreated rats

The ability of zinc (Zn) salts to induce the synthesis of metallothionein (MT) in liver, kidney and pancreas of rats pretreated with cadmium (Cd) salts was investigated. Twenty-four hours after either CdCl2 (2.0 mg Cd/kg, s.c.) or saline pretreatment, rats were injected with saline, CdCl2 (2.0 mg Cd/kg, s.c.) or ZnSO4 (20 mg Zn/kg, s.c.) and the concentrations of MT and MT-1 mRNA in tissues subsequently measured. After a single injection of Cd salts, concentrations of MT and MT-1 mRNA were significantly increased in liver as compared to control. With two injections of Cd, the accumulation of MT in liver was approximately twice the levels of MT following a single injection of Cd. In kidney, MT and MT-1 mRNA expression were significantly increased only after two injections of Cd and in the pancreas, Cd injections did not alter either MT content or MT-1 mRNA expression. Treatment with Zn salts increased MT concentrations in both liver and pancreas. However, the pancreas was the most responsive to injections of Zn salts as compared to the liver in terms of increases in both protein concentration and MT-1 mRNA expression. When Zn injection was preceded by a Cd injection, induction as measured by MT-1 mRNA and MT concentrations were approximately additive in liver. In kidney, although Cd or Zn treatment separately had no effect on MT or MT-1 mRNA content, injection of Cd followed by Zn resulted in significantly increased levels of renal MT and MT-1 mRNA. Fractionation of liver cytosols on a Sephadex G-75 column revealed that in animals receiving two injections of Cd, virtually all the Cd was associated with MT whereas Zn was distributed between both high molecular weight (HMW) proteins and MT. In animals receiving both Cd and Zn injections, cytosolic Cd was still bound predominantly to the MT fraction, while the proportion of cytosolic Zn associated with MT increased. The results of this study suggest that, treatment with Cd salts followed by Zn salt injection can induce further synthesis of MT in liver, kidney and pancreas with subsequent binding of both Zn and Cd to the intracellular MT.     

Cellular and biochemical response of the rat lung to repeated inhalation of cadmium

Male Lewis rats were exposed from 1 to 6 weeks (3 hr/day, 5 days/week) to a Cd aerosol (1.6 mg Cd/m3). After the first week, there were significant elevations in airway amounts of lactic dehydrogenase, alkaline and acid phosphatase, protein, and polymorphonuclear leucocytes. After 2 weeks of exposures, airway cytological and biochemical alterations intensified and pulmonary histopathology was observed. The severity of pulmonary injury did not progress beyond this point, although Cd continued to accumulate in the lung in a linear fashion. During the next 3 weeks of exposures, airway alterations diminished and lung histology became normal, suggesting that pulmonary adaptation to Cd might have occurred. Cd-binding proteins, with properties similar to hepatic metallothionein (MT), were isolated from the lungs of Cd-exposed animals. Pulmonary MT quantities increased significantly with repeated exposure to Cd. Sequestration of Cd by MT may be involved in the partial resolution of the lung injury. Translocation of Cd to the liver and kidney also occurred following inhalation exposure. Prior Cd inhalation exposure increased Cd translocation to the kidney, but not to the liver. Liver and kidney Cd burdens increased during the 6 weeks of Cd exposure. MT values also rose but hepatic MT quantities increased faster and to a greater extent than renal MT quantities.     

Metallothionein-null mice are more sensitive than wild-type mice to liver injury induced by repeated exposure to cadmium.

Liver is a major target organ of cadmium (Cd) toxicity following acute and chronic exposure. Metallothionein (MT), a low-molecular-weight, cysteine-rich, metal-binding protein has been shown to play an important role in protection against acute Cd-induced liver injury. This study investigates the role of MT in liver injury induced by repeated exposure to Cd. Wild-type and MT-I/II knockout (MT I/II-null) mice were injected sc with a wide range of CdCl(2) doses, 6 times/week, for up to 10 weeks, and their hepatic Cd content, hepatic MT concentration, and liver injury were examined. Repeated administration of CdCl(2) produced acute and nonspecific chronic inflammation in the parenchyma and portal tracts and around central veins. Higher doses produced granulomatous inflammation and proliferating nodules in liver parenchyma. Apoptosis and mitosis occurred concomitantly in liver following repeated Cd exposure, whereas necrosis was mild. As a result, significant elevation of serum enzyme levels was not observed. In wild-type mice, hepatic Cd concentration increased in a dose- and time-dependent manner, reaching 400 microgram/g liver, along with 150-fold increases in hepatic MT concentrations, the latter reaching 1200 microgram/g liver. In contrast, in MT I/II-null mice, hepatic Cd concentrations were about 10 microgram/g liver. Despite the lower accumulation of Cd in livers of MT I/II-null mice, the maximum tolerated dose of Cd was one-eighth lower than that for wild-type mice at 10 weeks, and liver injury was more pronounced in the MT I/II-null mice, as evidenced by increases in liver/body weight ratios and histopathological analyses. In conclusion, these data indicate that (1) nonspecific chronic inflammation, granulomatous inflammation, apoptosis, liver cell regeneration, and presumably, preneoplastic proliferating nodules are major features of liver injury induced by repeated Cd exposure, and (2) intracellular MT is an important protein protecting against this Cd-induced liver injury.     

Cadmium-induced hepatic and renal injury in chronically exposed rats: likely role of hepatic cadmium-metallothionein in nephrotoxicity

Rats were injected sc with 0.5 mg Cd/kg, 6 days/week, for up to 26 weeks. Hepatic and renal function and tissue Cd and metallothionein (MT) content were determined in tissues and plasma at various times after Cd injection. Cd in liver and kidney increased linearly for the first 10 weeks of treatment, but thereafter hepatic concentrations of Cd decreased by 33% whereas the content of Cd in kidney remained constant. MT in liver and kidney increased linearly during the first 12 weeks of Cd treatment to 4400 and 2300 micrograms MT/g, respectively, but rose only slightly thereafter. Circulating concentrations of MT progressively increased beginning 2 weeks after Cd treatment and were approximately 10 times control values in rats dosed with Cd for 12 or more weeks. Plasma activities of alanine and aspartate aminotransferase exhibited a time course similar to that observed with MT, and were elevated as early as the sixth week of Cd exposure. Sharp increases in activities of these enzymes also occurred after 10 to 12 weeks of dosing. Hepatic microsomal metabolism of benzo[a]pyrene and ethylmorphine was severely attenuated beginning 4 weeks after Cd. Renal injury occurred after hepatic damage, as evidenced by decreased in vitro p-aminohippuric acid uptake beginning 8 weeks after exposure. Urine outflow increased threefold 11 weeks after Cd exposure began, while urinary protein and Cd excretion increased beginning at Week 9. These data indicate the liver is a major target organ of chronic Cd poisoning, and suggest that Cd-induced hepatic injury, via release of Cd-MT, may play an important role in the nephrotoxicity observed in response to long-term exposure to Cd.     

Tissue distribution of cadmium in rats given minimum amounts of cadmium-polluted rice or cadmium chloride for 8 months.

To investigate the relationship between cadmium (Cd) toxicity, intestinal absorption, and its distribution to various tissues in rats treated orally with minimum amounts of Cd, 14 female rats per dose group per time point were given diets consisting of 28% purified diet and 72% ordinary rice containing Cd-polluted rice (0. 02, 0.04, 0.12, or 1.01 ppm of Cd) or CdCl(2) (5.08, 19.8, or 40.0 ppm of Cd) for up to 8 months. At 1, 4, and 8 months after the commencement of Cd treatment, seven rats per group were euthanized for pathological examinations to determine the Cd concentrations in the liver and kidneys and metallothionein (MT) in the liver, kidneys, intestinal mucosa, serum, and urine. One week before each period of 1, 4, and 8 months, the remaining seven rats in each group were administered a single dosage of (109)Cd, a tracer, to match the amounts of the designated Cd doses (about 1.2 to 2400 microg/kg body wt). They were euthanized 5 days later to determine the distribution of Cd to various tissues. No Cd-related toxic changes were observed. The concentrations of Cd in the liver and kidneys at any time point and MT in the liver, kidney, serum, and urine at 4 and 8 months increased dose-dependently, whereas MT in the intestinal mucosa did not alter markedly at any time point. The distribution rates of Cd to the liver increased dose-dependently (40% at lower doses to 60% at higher doses), whereas those to the kidney decreased dose-dependently (20% at lower doses to 10% at higher doses). The Cd retention rates 5 days after (109)Cd administration (amounts of Cd in various tissues/amounts of Cd administered) ranged from 0.2 to 1. 0% at any time point. These results suggest that the distribution of Cd to the liver and kidneys after the oral administration vary depending on the dosage levels of Cd. The difference of the distribution pattern of Cd to the liver and kidney is probably due to the difference in the form of the absorbed Cd, i.e., free ion or Cd-MT complex, although not closely related to the MT in the intestinal mucosa.     

Health effects of low-level cadmium intake and the role of metallothionein on cadmium transport from mother rats to fetus

Female Wistar rats were given Cd (as CdCl(2)) at a dose of 0, 1, 2, and 5 mgCd/kg/day by gastric tube daily for 6 consecutive days each week for 10 weeks. After the birth, newborn rats were sacrificed on day 1 and at 4 weeks. Mother rats were sacrificed after 4 weeks of lactation The concentrations of Cd in uterus and placenta, and metallothionein (MT) in the uterus of mother rats were determined. The concentrations of Cd in kidney and liver of newborn rats were also determined. Expression of iso-MT genes (I, II, and III) in the uterus of mother rats was measured using RT-PCR. The Cd concentration in the liver of newborn rats at the first day after birth was higher than in the kidney, while the concentration in the kidney of newborn rats at the fourth week after the birth was significantly higher than in the liver. The uterine MT concentration increased with accumulation of Cd; however, the MT concentration did not increase enough to prevent Cd transport to the fetus. On the other hand, it was considered that more Cd was transported as the chemical form of nonMT-Cd from mother rat, and accumulated in the liver rather than kidney of the fetus. Based on analyses of the Cd distribution in the liver and kidney of newborn rats, we speculate that MT in the uterus and placenta does not play a significant role in preventing Cd transport through the placenta from the uterus to the fetus.