Concentration Of Metallothionein In Liver Research Articles

Effect of dietary zinc pectin oligosaccharides chelate on growth performance, enzyme activities, Zn accumulation, metallothionein concentration, and gene expression of Zn transporters in broiler chickens1.

This study was to investigate the effect of zinc pectin oligosaccharides chelate (Zn-POS) on growth performance, serum enzyme activities, tissue zinc accumulation, metallothionein (MT) concentrations, and gene expression of zinc transporters (ZnT) in broilers. Five hundred forty 1-d-old Arbor Acres broiler chicks were randomly assigned to 5 dietary groups with 6 replicates of 18 birds per replicate. The diets were formulated with the same supplemental Zn level (80 mg/kg diet) but different amount of the Zn-POS: 0, 200, 400, 600, and 800 mg Zn-POS/kg diet. ZnSO4 was used to adjust to the desired amount of the Zn (80 mg/kg) in the Zn-POS diets. Broilers were fed with the experimental diets for 42 d including the starter (days 1 to 21) and grower (days 22 to 42) phases. Our results showed that dietary supplementation of Zn-POS linearly and quadratically increased (P < 0.05) the average daily gain and gain-to-feed ratio during 22 to 42 d and 1 to 42 d as well as body weight on day 42, whereas reduced (P < 0.05) the sum of mortality and lag abnormalities in broilers on day 42. Besides, serum alkaline phosphatase and copper-zinc superoxide dismutase activities increased (P < 0.05) linearly and quadratically in response to dietary Zn-POS supplemental level on day 42. Dietary Zn-POS supplementation increased Zn accumulation in serum (linear, P < 0.05), liver (linear, P < 0.05), and pancreas (linear and quadratic, P < 0.05). In addition, Zn-POS supplementation linearly and quadratically increased (P < 0.01, P < 0.05, respectively) MT concentrations in liver and pancreas of broilers. Pancreatic mRNA levels of MT, ZnT-1, and ZnT-2 increased (P < 0.05) linearly and quadratically, and the mRNA expression of metal response element-binding transcription factor-1 increased linearly (P < 0.05), in response to dietary Zn-POS supplementation. In conclusion, supplementation of Zn-POS in the diet increases Zn enrichment in the metabolic organs such as liver and pancreas and promotes productive performance in broilers.

Effects of Maternal Zinc Glycine on Mortality, Zinc Concentration, and Antioxidant Status in a Developing Embryo and 1-Day-Old Chick.

This study was conducted to investigate the effects of maternal zinc glycine (Zn-Gly) supplementation as an alternative for zinc sulfate (ZnSO4) on mortality, zinc (Zn) concentration, and antioxidant status in a developing embryo and 1-day-old chick. Six hundred 39-week-old broiler breeders were randomly assigned to 6 treatments, each treatment including 5 replicates with 20 birds each. Six treatments received a basal diet (control, 24mg Zn/kg diet) or a basal diet supplemented with ZnSO4 (80mg Zn/kg) or Zn-Gly (20, 40, 60, or 80mg Zn/kg), respectively. The experiment lasted for 8weeks after a 4-week pre-experiment with a basal diet. At the last week, 100 eggs per replicate were randomly collected for incubation. Compared with the control treatment, Zn supplementation decreased (P<0.05) embryo mortalities of the late stage and the whole period, increased (P<0.05) liver Zn concentration in the embryo of d9, d19, and 1-day-old chick, and improved (P<0.05) antioxidant status in the embryo of d19 and 1-day-old chick. Compared with the ZnSO4 treatment, 80mg Zn/kg Zn-Gly treatment significantly decreased (P<0.05) the late stage embryo mortality and increased (P<0.05) liver Zn concentration in the embryo of d9, d19, and 1-day-old chick. The 80mg Zn/kg Zn-Gly treatment significantly increased (P<0.05) copper-zinc superoxide dismutase activity in d19 embryo and 1-day-old chick, total superoxide dismutase activity in 1-day-old chick, and copper-zinc superoxide dismutase messenger RNA (mRNA) abundance of d9 embryo and 1-day-old chick than that in ZnSO4 treatment. The liver metallothionein concentration of the developing embryo and 1-day-old chick and its mRNA abundance of d19 embryo were also significantly increased (P<0.05) in the 80mg Zn/kg Zn-Gly treatment in comparison with ZnSO4 treatment. In conclusion, maternal Zn supplementation decreased embryo mortalities of the late stage and the whole period by increasing liver Zn concentration and antioxidant status in d19 embryo and 1-day-old chick, and 80mg Zn/kg from Zn-Gly treatment was the optimum choice.

Effects of Zinc Glycinate on Productive and Reproductive Performance, Zinc Concentration and Antioxidant Status in Broiler Breeders.

An experiment was conducted to investigate the effects of zinc glycinate (Zn-Gly) supplementation as an alternative for zinc sulphate (ZnSO4) on productive and reproductive performance, zinc (Zn) concentration and antioxidant status in broiler breeders. Six hundred 39-week-old Lingnan Yellow broiler breeders were randomly assigned to 6 groups consisting of 4 replicates with 25 birds each. Breeders were fed a basal diet (control group, 24mg Zn/kg diet), basal diet supplemented with 80mg Zn/kg diet from ZnSO4 or basal diet supplemented with 20, 40, 60 and 80mg Zn/kg diet from Zn-Gly. The experiment lasted for 8weeks after a 4-week pre-test with the basal diet, respectively. Results showed that Zn supplementation, regardless of sources, improved (P < 0.05) the feed conversion ratio (kilogram of feed/kilogram of egg) and decreased broken egg rate, and elevated (P < 0.05) the qualified chick rate. Compared with the ZnSO4 group, the 80mg Zn/kg Zn-Gly group significantly increased (P < 0.05) average egg weight, fertility, hatchability and qualified chick rate, whereas it decreased (P < 0.05) broken egg rate. The Zn concentrations in liver and muscle were significantly higher (P < 0.05) in 80mg Zn/kg Zn-Gly group than that in ZnSO4 group. Compared with ZnSO4 group, 80mg Zn/kg Zn-Gly group significantly elevated (P < 0.05) the mRNA abundances of metallothionein (MT) and copper-zinc superoxide (Cu-Zn SOD), as well as the Cu-Zn SOD activity and MT concentration in liver. Moreover, the 80mg Zn/kg Zn-Gly group had higher (P < 0.05) serum T-SOD and Cu-Zn SOD activities than that in the ZnSO4 group. This study indicated that supplementation of Zn in basal diet improved productive and reproductive performance, Zn concentration and antioxidant status in broiler breeders, and the 80mg Zn/kg from Zn-Gly was the optimum choice for broiler breeders compared with other levels of Zn from Zn-Gly and 80mg/kg Zn from ZnSO4.

Impact of cadmium on the level of hepatic metallothioneins, essential elements, and selected enzymes in the experimental rat model

The response of different strains of laboratory rats (Rattus norvegicus L.) on both acute (via intraperitoneal injection) and chronic (via drinking water and/or diet) cadmium intoxication was investigated in the model study. The rat strains Long Evans (LE), Spontaneously hypertensive rat (SHR), and Brown Norway (BN) were tested and compared, and total Cd levels and metallothionein (MT) concentrations were determined in the liver of experimental animals. The liver MT concentrations were determined by using adsorptive chronopotentiometry and modified Brdička reaction and were significantly correlated (r = 0.965) with the total liver Cd content. Moreover, the Cd application resulted in increasing zinc liver contents confirming intensive MT synthesis in the rat liver. In the blood plasma, specific enzymatic activity of glutathione reductase (GR) and glutathione-S-transferase (GST) was determined suggesting increasing activity of GR with the amount of applied Cd for all three strains, whereas ambiguous results have been found for the activity of GST. Therefore, MT concentrations seemed to be more sensitive indicators of the Cd intoxication compared to the assessment of the specific enzymatic activity. &amp;nbsp;

The involvement of metallothionein in hepatic and renal Cd, Cu and Zn accumulation in pigs

This study investigated the involvement of metallothionein (MT) in hepatic and renal cadmium (Cd) accumulation and the interactions of this element with the essential elements copper (Cu) and zinc (Zn) in pigs receiving diets with or without Cu and Zn supplementation, in intensive and extensive production systems respectively. Animals from intensive systems showed significantly higher Cd concentrations in the liver (83.3μg/kg wet weight) and kidney (343μg/kg) than animals from extensive systems (33.2 and 130μg/kg respectively). Cu (liver 16.9, kidney 5.52mg/kg) and Zn (82.8 and 29.7mg/kg) concentrations were also significantly higher in pigs from intensive than in animals from extensive systems (Cu 10.1 and 4.64mg/kg, Zn 66.2 and 23.1mg/kg). Pigs from intensive systems showed 50% higher kidney MT concentrations than animals from extensive systems (278 and 183mg/kg respectively), whereas liver MT concentrations were very similar in the two groups (1696 and 1517mg/kg respectively). MT concentrations in both the liver and the kidney were strongly dependent on the Zn status of the animal. In the liver neither Cu nor Cd displaced Zn from MT, and the proportion of MT binding sites apparently occupied by Cu and Cd decreased with increasing hepatic MT concentration, despite the fact that both Cu and Cd have higher affinity for MT than Zn. The proportion of MT binding sites occupied by Cu and Cd was also directly related to Zn:Cu ratio in hepatic cells. In the kidney, in contrast, Cu seems able to compete with Zn for MT binding sites, and the proportion of MT binding sites occupied by Cu increased with increasing renal MT concentration.

Effects of malathion and cadmium on acetylcholinesterase activity and metallothionein levels in the fish Seriola dumerilli

The potential use of acetylcholinesterase (AChE) and metallothionein (MT) responses as biomarker of organophosphorous (OPs) and trace metal were assessed in fish Seriola dumerilli exposed to 0, 4, 6 mg/kg of malathion for 2, 7 and 13 days, and to 0, 50, 100, 250 mug/kg of Cd for 2 days. Brain AChE was significantly inhibited after 2 and 7 days of malathion exposure, in a dose-response manner, but no inhibition was observed after 13 days of exposure. When exposed to Cd for 2 days, S. dumerelli presented an increase in AChE activity at a concentration of 50 mug/kg, but a strong and dose-dependent AChE inhibition at 100 and 250 mug/kg. Cd treatment also caused a rapid increase in MTs concentration in liver, even at the lower concentration. Our experiments indicate that the measurement of hepatic MT concentration and brain AChE activity in S. dumerilli would be useful biomarkers of OP and Cd exposure and/or effects.

Effects of Salmonella typhymurium Lipopolysaccharide Challenge on the Performance, Immune Responses and Zinc Metabolism of Laying Hens Supplemented with Two Zinc Sources

The study was conducted to determine the effect of Salmonella typhymurium lipopolysaccharide (LPS) challenge on egg-laying performance, inflammatory response, zinc metabolism in layer fed diets supplemented with organic or inorganic zinc since 3- wk-old. The three dietary treatments were corn-soybean meal basal diet without supplemental zinc or with supplemental zinc at 60 mg/kg zinc from ZnSO4 or zinc amino acid complex (ZnAA). At the age of 58 wk-old, twelve hens from each dietary treatment were allotted into two sub-groups. On day 1, 3, 5, 7 of the 58 th week of age, six birds of one sub-group were injected intraperitoneally (i.p.) with 2 ml LPS (1.0 µg/ml) or sterile saline. Neither zinc source × immune challenge interaction nor zinc source effect on egg production performance was observed (p>0.05), LPS-challenge decreased egg production (p 0.05). Supplementation of 60 mg/kg zinc from either ZnAA or ZnSO4 significantly (p<0.05) elevated metallothionein (MT) concentration in liver and spleen. MT concentration in liver of birds fed ZnAA diet was higher than in those fed ZnSO4 diet (p<0.05). The magnitude of increase of hepatic and splenic MT due to LPS challenge was higher by supplementation of ZnAA than ZnSO4. The results suggest that zinc amino acid complex enhanceed MT synthesis and zinc sequestered in liver and spleen and increased the sensitivity to immune response due to LPS challenge. (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 12 : 1717-1724)

Zinc treatment prevents lipopolysaccharide‐induced teratogenicity in mice

During pregnancy, exposure to lipopolysaccharide (LPS) can lead to abortion, preterm delivery, and teratogenicity. The mechanisms underlying these effects are unclear. Both LPS and ethanol are potent inducers of liver metallothionein (MT), a key Zn binding protein. The teratogenic effects of ethanol have been linked to MT-induced changes in maternal-fetal Zn homeostasis, leading tofetal deficiency. This study was designed to assess whether the teratogenic effects of LPS are also related to MT induction and changes in Zn homeostasis. Non-pregnant normal (MT +/+) and MT-null (MT -/-) mice were injected subcutaneously with 0.5 microg/gm LPS and killed over 48 hr. In MT +/+ mice, liver MT concentrations were elevated from 6 hr, and were maximal at 24 hr (30-fold basal), whereas liver Zn levels were also increased from 6 hr. Plasma Zn concentrations decreased by 80% at 6 hr, and were below normal between 6 and 24 hr. In MT -/- mice, plasma Zn levels were increased from basal between 6 and 16 hr. Dams were injected with LPS, saline, or LPS and ZnSO4 (2 microg/gm, MT +/+ only) on Day 8 of gestation (GDS), killed on GD18, and the fetuses examined for malformations. External abnormalities were most prevalent in fetuses from MT +/+ dams exposed to LPS, where 34% of fetuses in each litterwere affected. MT +/+ dams treated with LPS and ZnSO4, and MT -/- dams treated with LPS had litters in which 5.4 and 4.8% of fetuses were abnormal respectively. The findings of this study strongly support the hypothesis that LPS teratogenicity is mediated at least in part by MT-induced changes in maternal Zn homeostasis,which compromises fetal Zn supply.

Waterborne ethynylestradiol induces vitellogenin and alters metallothionein expression in lake trout ( Salvelinus namaycush)

Estrogenic contaminants isolated from waters receiving sewage treatment plant effluents are known to induce the egg yolk precursor vitellogenin (VTG) in male fish. Levels of the metal binding protein metallothionein (MT) have also been shown to be affected by estrogens in fish. It has been postulated that MT declines in estrogen exposed fish to facilitate transfer of the essential metal Zn to cellular components required for VTG synthesis. To examine the changes in MT and VTG concentrations in fish exposed to an estrogen contaminant, lake trout ( Salvelinus namaycush) were exposed to waterborne ethynylestradiol at 0, 4, 40 or 400 ng/l −1 for 21 days. Blood and tissues were collected after 21 days of exposure to measure circulating levels of VTG as well as MT concentrations in liver and kidney. VTG increased in male and female fish from all three exposure groups compared to control fish. MT in liver significantly decreased in males and females compared to the controls, in the two highest exposures. MT in kidney was significantly higher in both sexes of fish exposed to the two highest concentrations of ethynylestradiol. These data are supportive of a relationship between estrogen exposure and the regulation of MT. Further studies to examine the specific links between estrogen exposure, VTG induction and regulation of essential metals like Zn are required.

Dietary Zinc Deficiency and Repletion Modulate Metallothionein Immunolocalization and Concentration in Small Intestine and Liver of Rats

Metallothionein (MT) functions in zinc (Zn) homeostasis and dietary Zn affects tissue MT concentration. The objective of this study was to investigate the effects of dietary Zn deficiency and 24-h Zn repletion on MT immunolocalization and concentration in the small intestine and liver of growing rats. Three-week-old rats fed Zn-deficient diet (< 1 mg Zn/kg) for 16 d had no MT staining in either small intestine or liver. After 24-h Zn repletion with control diet (30 mg Zn/kg), strong MT staining was observed in intestinal Paneth cells and surface epithelial cells in the proliferative regions of villi. Pair-fed control rats had strong MT staining in liver that was localized around central veins. After 24-h energy repletion, the hepatic MT staining diminished. Furthermore, Zn-deficient rats had significantly reduced intestinal (57%) and hepatic (61%) MT concentrations but unaffected Zn concentrations compared with controls that consumed food ad libitum. Zn repletion for 24 h restored intestinal and hepatic MT concentrations and reduced hepatic Zn concentration. Pair-fed control rats had elevated MT concentration in liver that was normalized by energy repletion. There was a significant positive correlation between tissue Zn and MT concentrations in liver (r = 0.60, P = 0.0001), but not in small intestine. In summary, MT immunolocalization and concentration in rat small intestine and liver were responsive to changes in Zn status, supporting the role of MT in Zn metabolism. Cell-type-specific localization of MT in small intestine after dietary Zn manipulations indicates a function of Zn and MT in gut immunity and intestinal mucosal turnover, and the pattern of hepatic MT distribution with energy restriction may be linked to detoxification processes.

Maternal Ethanol Exposure Is Associated With Decreased Plasma Zinc and Increased Fetal Abnormalities in Normal but Not Metallothionein‐Null Mice

Ethanol profoundly affects fetal development, and this is proposed to be due primarily to a transient fetal zinc (Zn) deficiency that arises from the binding of Zn by metallothionein (MT) in the maternal liver. Zn homeostasis and fetal outcome were investigated in normal (MT+/+) and metallothionein-null (MT-/-) mice in response to ethanol exposure. Mice were treated with saline or ethanol (0.015 m/g intraperitoneally at 0 and 4 hr) on day 8 of gestation (Gd8), and the degree of fetal dysmorphology was assessed on Gd18. The incidence of external abnormalities was significantly increased in offspring from MT+/+ dams exposed to ethanol, where 27.4% of fetuses were affected. MT-/- ethanol-, MT+/+ saline-, and MT-/- saline-treated dams had fetuses in which the frequencies of abnormalities were 2.2, 6.4, and 6.9%, respectively. To investigate Zn homeostasis, nonpregnant mice were killed at intervals over 16 hr after ethanol injection. Liver MT concentrations in MT+/+ mice were increased 20-fold by 16 hr, with a significant elevation evident by 4 hr, whereas liver Zn levels were also significantly increased by 2 hr and maintained for 16 hr. In parallel with these changes, plasma Zn concentrations in MT+/+ mice decreased by 65%, with minimum levels of 4.5+/-0.3 micromol/liter at 8 hr. Conversely, MT-/- mice exhibited increased plasma Zn concentrations, with peak values of 20.8+/-0.3 observed at 4 hr. These findings link the teratogenic effect of ethanol to the induction of maternal MT and the limitation of fetal Zn supply from the plasma.

Chemical characteristics and relative bioavailability of supplemental organic zinc sources for poultry and ruminants.

Eight commercially available organic Zn products and reagent-grade ZnSO4 x 7H2O (Zn Sulf) were evaluated by polarographic analysis, and solubility in .1 M K2HPO4-KH2PO4 buffer (pH 5), .2 M HCl-KCl buffer (pH 2), and deionized water. Fractions from these solubility tests were evaluated by gel filtration chromatography for structural integrity. Degree of chelation was generally positively related to chelation effectiveness determined by polarography. The organic sources were Zn methionine complex A (Zn MetA), Zn methionine complex B (Zn MetB), Zn polysaccharide complex (Zn Poly), Zn lysine complex (Zn Lys), Zn amino acid chelate (Zn AA), Zn proteinate A (Zn ProA), Zn proteinate B (Zn ProB), and Zn proteinate C (Zn ProC). Three experiments were conducted to estimate the relative bioavailability of Zn from the organic Zn supplements for chicks and lambs when added at high dietary levels to practical diets. Bone Zn concentration increased (P < .001) as dietary Zn increased in both experiments. When Zn Sulf was assigned a value of 100% as the standard, multiple linear regression slope ratios of bone Zn from chicks fed 3 wk regressed on dietary Zn intake gave estimated relative bioavailability values of 83 +/- 14.6 and 139 +/- 16.9 for Zn AA and Zn ProA, respectively, in Exp. 1 and 94 +/- 11.6, 99 +/- 8.8, and 108 +/- 11.4 for Zn Poly, Zn ProB, and Zn ProC, respectively, in Exp. 2. In Exp. 3, 42 lambs were fed diets containing Zn Sulf, Zn ProA, Zn AA, or Zn MetB for 21 d. Based on multiple linear regression slope ratios of liver, kidney, and pancreas Zn and liver metallothionein concentrations on added dietary Zn, bioavailability estimates relative to 100% for Zn Sulf were 130, 110, and 113 for Zn ProA, Zn AA, and Zn MetB, respectively. Except for Zn ProA, which was greater, the organic Zn supplements had bioavailability values similar to that of Zn Sulf for chicks and lambs. Bioavailability of organic Zn products was inversely related to solubility of Zn in pH 5 buffer in chicks (r2 = .91) and pH 2 buffer in lambs (r2 = .91), but not to an estimate of degree of chelation.

Chromium increases pancreatic metallothionein in the rat

The ability of chromium (Cr) salts to increase metallothionein (MT) levels in rat liver, kidney and pancreas, and its relationship with the presence of toxic effects are reported here. Rats were injected subcutaneously with 0, 10, 20, 30, 40, or 50 mg K 2Cr 2O 7/kg and sacrificed 24 h later. Total Cr accumulation followed a dose-dependent pattern, levels in kidney being higher than those in liver or pancreas, suggesting different tissue bioavailabilities and accumulation patterns. Cr(IV) administration resulted in a tissue-specific MT induction: pancreas and liver showed five- and 3.5-fold MT increases, respectively; no increase was observed in the kidney. A positive correlation was observed between zinc and MT concentrations in liver, and between total Cr and MT concentrations in pancreas. Serum α-amylase activity showed a dose-dependent increase starting from 20 mg/kg, whereas serum glucose levels increased at doses higher than 30 mg/kg. Serum aspartate aminotransferase and alanine aminotransferase activities were increased in a dose-dependent manner, from 20 and 30 mg/kg, respectively. Our results showed that treatment with Cr(VI) can induce MT synthesis in pancreas and suggests a subsequent binding of Cr to MT. Also, pancreas is a target organ for Cr toxicity, and the usefulness of α-amylase activity as a sensitive biomarker of Cr toxicity in human exposed populations merits further study.

Liver Metallothionein Level and Metal Content in Fish of Chung-Kung Stream, Taiwan-Tilapia andLiza Macrolepsis

Abstract A survey of Chung-Kung sttream fish was undertaken on six occasions from March 1994 to August 1995. Tilapia (Oreochromis hybrid) and Liza macrolepsis were the major species found downstream and were chosen as the target species for metallothionein (MT) analysis of liver tissue. in total MT of 77 tilapia and 48 Liza macrolepsis liver samples were analyzed. Significantly higher values (p >0.05) were found for the August 1995 samples than for samples taken earlier at site B (6 km from the sea) for tilapia and at site A (estuary) for Liza macrolepsis. Liver zinc, copper and cadmium were analyzed for the 1995 samples. for tilapia, liver MT concentration was found to correlate well with zinc concentration (r = 0.84, p > 0.001). for Liza macrolepsis, good correlation was found for MT with both zinc (r = 0.89, p > 0.001) and copper (r = 0.90, p > 0.001). These results indicate that in the Chung-Kung stream, zinc and copper may be the major inducers of fish liver MT. Since these two species are ubiquitous in tropical areas, they would provide a good biomarker for evaluation of integrated metal exposure in the tropical aquatic environment.

Naturally high levels of zinc and metallothionein in liver of several species of the squirrelfish family from Queensland, Australia

Recently, we found that liver of squirrelfish (Holocentrus rufus) from Bermuda contains remarkably high concentrations of metallothionein (MT) and Zn. To clarify the nature and cause of the Zn accumulation, four Holocentridae species from three genera (Neoniphon sammara, Sargocentron spiniferum, Myripristis violacea, and Myripristis murdjan) were collected from a totally different area, the Great Barrier Reef, Australia. The average hepatic Zn levels in these species ranged from 67 μg g-1 (S. spiniferum) to 1000 μg g-1 (N. sammara). The intraspecies variation in the hepatic Zn level was pronounced. In both N. sammara and M. murdjan, there was a 48-fold difference between the lowest and the highest Zn concentration. Zn accumulation was closely correlated to a dramatically elevated concentration of MT in liver. In N. sammara, which possessed the highest level of MT among the investigated species, the mean hepatic MT concentration was 19 500 μg g-1. Subcellular fractionation of the liver showed that MT was responsible for the binding of up to 74% of the hepatic Zn. The concentrations of MT and Zn in gills were low, suggesting that Zn storage in fish within this family is tissue-specific. The results further indicate that the high concentrations of MT and Zn in Holocentridae liver are linked to normal physiological processes. We suggest that the Holocentridae family may be a unique model for future studies of Zn metabolism and the function of MT.

Protection against cadmium-metallothionein nephrotoxicity in streptozotocin-induced diabetic rats: role of increased metallothionein synthesis induced by streptozotocin

Protection against the development of nephrotoxicity following the administration of cadmium-metallothionein (CdMT) at a dose of 0.4 mg Cd per kg body weights was studied in streptozotocin (STZ)-induced diabetic rats. Six groups of Wistar male rats were used (Groups A and B, Groups Al and C, and Groups A2 and D were injected intraperitoneally with STZ at doses of 0, 50 and 100 mg/kg, respectively, and then 6 days later, Groups B, C and D were injected subcutaneously with CdMT). Proteinuria, albuminuria and transferrinuria were observed after the administration of CdMT, and a dose-related decrease following the increased STZ dose was seen in Groups B, C and D. The concentrations of metallothionein (MT) and zinc (Zn) in liver and kidney were dose-dependently increased in Groups B, C and D. Induction of increased MT synthesis in liver and kidney as the result of the STZ treatment was observed in this study. In particular, a remarkable increase in liver MT concentration was induced by STZ, and transport to the kidney of MT synthesized in liver may perhaps explain the protection against cadmium nephrotoxicity in STZ-induced diabetic rats.

Altered maternal zinc metabolism following exposure to diverse developmental toxicants

It has been hypothesized that one mechanism contributing to the developmental toxicity of some xenobiotics is an embryonic/fetal zinc (Zn) deficiency that occurs secondary to toxicant-induced changes in maternal Zn metabolism. We studied the influence of diverse toxicants (urethane, ethanol, melphalan, arsenic, and α-hederin) on maternal-embryonic Zn metabolism and maternal liver metallothionein (MT) induction in Sprague-Dawley rats given a 65Zn-labelled meal by gavage 8 h after toxicant exposure and killed 10 h later on gestation day 12.5. Exposure to the toxicants resulted in increases in maternal hepatic MT concentrations that generally exceeded that which could be accounted for by reductions in food intake. 65Zinc retention was higher in maternal liver and lower in the products of conception in the toxicant-exposed groups. Strong linear relationships were found; as maternal liver MT concentrations increased, 65Zn retention in maternal liver was increased and 65Zn distribution to the conceptuses was decreased. These results support the hypothesis that diverse insults can produce developmental toxicity, in part, by altering maternal and embryonic Zn metabolism.

Alterations in Intestinal Uptake and Compartmentalization of Zinc in Response to Short-Term Dexamethasone Therapy or Excess Dietary Zinc in Piglets

Premature infants receive high dietary zinc and often glucocorticoids as a treatment for chronic lung disease. A piglet model was developed to investigate intestinal zinc transport and distribution of tissue zinc in response to treatment with short-term (5 d) glucocorticoid therapy or a high zinc diet. Piglets (13-15 d old; n = 21) were randomly allocated to: 1) dexamethasone (DEX) therapy (1.5 mg/kg intramuscularly twice a day), 2) high zinc diet (15.3 mmol/kg), or 3) control group (0.3 mmol dietary zinc/kg and saline intramuscularly twice a day). Pig weight, formula intake, urine volume, and blood glucose were monitored. At necropsy, tissue samples were obtained to measure zinc in plasma and zinc and metallothionein in liver and small intestinal mucosa. Velocity of zinc uptake by intestinal brush border membrane vesicles was measured using 65Zn tracer. Maximum uptake rate and Km for zinc uptake by brush border membrane vesicles were significantly greater (p < 0.05) in DEX compared with control and high zinc groups. DEX-treated piglets had a significantly lower (p < 0.05) zinc efflux rate across brush border membrane vesicles compared with that of the control. The high zinc group had a higher liver (p < 0.05) and mucosal (p < 0.05) zinc content and higher liver metallothionein concentration (p < 0.001) compared with the control and DEX groups. Weight gain over 5 d was not different among groups. Daily blood glucose was higher (p < 0.05) in DEX versus control and high zinc groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Examination of potential mechanism(s) of metallothionein induction by diethyl maleate

Diethyl maleate (DEM) is a glutathione-depleting agent that can increase the levels of the sulfhydryl-rich protein metallothionein (MT) in liver. The purpose of the present study was to examine the mechanism(s) by which DEM increases mouse hepatic MT levels. DEM appears to be an indirect MT inducer as suggested by the lack of increase in MT levels when cultured mouse hepatocytes were exposed to DEM. Four possible mechanisms by which indirect MT inducers may cause an elevation in MT concentrations in liver were examined. Zn levels did not increase prior to the increase in hepatic MT, thus, a Zn redistribution to the liver is not the cause of the liver MT induction by DEM. The adrenal gland products were not required for MT induction in liver, as adrenalectomy did not abolish the increase in hepatic MT caused by DEM. The elevation in liver MT does not appear to be due solely to the decrease in liver glutathione (60%) in the initial hour after DEM, because phorone, which decreases liver glutathione (80%), produced only a fourfold increase in hepatic MT. Activation of macrophages does not seem to account for the rise in liver MT levels, as there was no increase in abundance of cytokine mRNAs for TNF-α, IL-1β, or IL-6 in the liver. These data suggest that the induction of hepatic MT by DEM does not occur in response to (1) an increase in liver Zn that precedes the increase in liver MT, (2) release of adrenal gland products, (3) decrease in liver glutathione, or (4) increased cytokine gene expression.

Metallothionein concentration in the liver of patients with Wilson's disease, primary biliary cirrhosis, and liver metastasis of colorectal cancer

In patients with primary biliary cirrhosis and Wilson's disease liver copper concentrations become elevated during the evolution of the disorder. The accumulated copper is thought to be detoxified by metallothionein, a protein which binds copper and zinc. In liver metastasis of colorectal cancer, copper and zinc concentrations are usually decreased compared to normal liver tissue, but little is known about the concomitant metallothionein levels. In the present study metallothionein concentrations were determined in archival liver samples from patients with primary biliary cirrhosis and Wilson's disease, and in both normal and malignancy-containing liver samples from patients with metastasis from a colorectal adenocarcinoma. Twenty-seven control liver samples contained 3.98±1.55 mg metallothionein/g protein. From the 21 liver samples of patients with primary library cirrhosis, which had a mean metallothionein concentration of 6.06±5.03 mg/g protein, 6 were above the highest control level. Liver metallothionein concentrations for the 8 patients with Wilson's disease were significantly elevated (10.98±6.93 mg/g protein, p<0.005 vs. controls and p<0.05 vs. primary biliary cirrhosis). In the 11 liver metastases from colorectal adenocarcinomas metallothionein concentrations (1.17±0.90 mg/g protein) were significantly (p<0.005) lower than surrounding normal liver tissue (4.25±1.75 mg/g protein). We conclude that in primary biliary cirrhosis and Wilson's disease increased liver metallothionein concentrations may detoxify the accumulated copper. Furthermore, liver metastasis of colorectal cancer contains less metallothionein than the surrounding normal liver tissue.