metallothionein and Metal-Metabolism--Inborn-Errors

Topics: Animals; Copper; Drug Interactions; Humans; Metal Metabolism, Inborn Errors; Metallothionein; Nutritional Physiological Phenomena; Zinc

The biochemistry of the essential trace element copper has been outlined. Following absorption, Cu(II) is transported by serum albumin and transcuprein to the liver where it is incorporated into the plasma Cu-protein, ceruloplasmin, or, possibly, stored as Cu-metallothionein or as superoxide dismutase. Ceruloplasmin is the long-term copper transporter and carries Cu(II) to the tissues for the biosynthesis of key Cu(II) enzymes, especially cytochrome c oxidase, lysyl oxidase and others. The production of copper enzymes raises many new questions about the metabolism of copper. Since ceruloplasmin is the centerpiece of copper metabolism and function, we conclude with more details on its chemistry and multifunctions. This Cu-protein of 132,000 daltons has now been totally sequenced and the copper-containing active sites located. Finally, we have proposed seven possible functions for ceruloplasmin, and there is now good evidence for the existence of ceruloplasmin receptors to expedite some of these functions.

Topics: Adult; Animals; Biological Transport; Carrier Proteins; Ceruloplasmin; Copper; Humans; Metal Metabolism, Inborn Errors; Metallothionein; Oxidoreductases; Receptors, Cell Surface; Receptors, Immunologic; Receptors, Peptide; Trace Elements

A review is presented of various aspects of copper (Cu) metabolism. The Cu absorption from the gastrointestinal tract in monogastric animals differs from that in ruminants. This is influenced by Cu binding compounds, sulphide production in the rumen, and molybdenum and zinc concentrations of the diet. Moreover, the valence of the Cu ions may influence the availability of Cu in the intestine. Metallothionein and lysosomes are involved in the accumulation of copper in the liver. The different findings in various Cu storage diseases may reflect different mechanisms of disease. Cu-induced liver cell damage and haemolysis may be the result of lipid peroxidation.

Topics: Animals; Cattle; Cattle Diseases; Ceruloplasmin; Chemical and Drug Induced Liver Injury; Copper; Digestive System; Dog Diseases; Dogs; Female; Hemolysis; Intestinal Absorption; Kinetics; Liver; Liver Diseases; Lysosomes; Metal Metabolism, Inborn Errors; Metallothionein; Mice; Rats; Rumen; Sheep; Sheep Diseases

Long-Evans Cinnamon (LEC) rats aged 16 +/- 4 weeks with histopathological alterations of liver and kidney, exhibited elevated Cu levels in liver, kidney and spleen which were 52, 27 and 5 times higher than those of the respective tissues of age-matched Wistar rats. About 61% of hepatic and about 38% of renal Cu was recovered in the cytosolic fraction. Metallothionein (MT) levels were found to correlate with the cytosolic Cu concentrations in liver and kidney. According to differential MT analysis, about 68 and 82% of hepatic and renal MT was loaded with Cu. The portion of MT which binds Cu was negatively correlated with the ratio of cytosolic Zn/Cu in all organs investigated. Despite high MT levels and the high percentage of Cu binding to MT, particularly in liver and kidney, considerable amounts of Cu remained unbound to MT. This non-MT bound Cu showed good correlation with the total cytosolic Cu content, and might play a crucial role in the pathogenesis of Cu toxicosis.

Topics: Animals; Copper; Cytosol; Female; Kidney; Male; Metal Metabolism, Inborn Errors; Metallothionein; Rats; Rats, Mutant Strains; Rats, Wistar; Spleen

Recently it was found that the clinical features of the LEC rat closely resemble those of human Wilson's disease. One of the characteristics of the animal is low levels of serum ceruloplasmin. Therefore, by using LEC rats, we attempted to define molecular basis of the deficiency in active site of ceruloplasmin in Wilson's disease patients. We made 3 monoclonal antibodies, ID2 against active site of ceruloplasmin, ID1 against inactive site of ceruloplasmin, and the remaining one against metallothionein. Using these monoclonal antibodies, we examined immunohistochemical stainings of LEC rat liver tissues, and compared them with those of LEA rats, as a control. ID1 stained the hepatocytes of both LEA and LEC rats, whereas ID2 stained LEA rat hepatocytes only. The results indicated that the ceruloplasmin secreted by LEC rat hepatocytes is mostly in inactive form. The antibody against metallothionein stained LEA rat hepatocytes only. This finding may also indicate that LEC rat hepatocytes express less amount of metallothionein than those of LEA rats.

Topics: Animals; Antibodies, Monoclonal; Binding Sites; Ceruloplasmin; Copper; Female; Hepatolenticular Degeneration; Humans; Immunohistochemistry; Liver; Male; Metal Metabolism, Inborn Errors; Metallothionein; Rats; Rats, Mutant Strains

The concentrations of copper, zinc and metallothionein-I (MT-I) mRNA were determined in the liver, kidney and brain of the brindled mutant mouse from birth until the time of death. Despite accumulation of copper in the kidney of the mutant, MT-I mRNA concentrations were normal. There was no difference between the MT-I mRNA in the brain of mutant and normal in the first 10 days of life, but after day 10 metallothionein mRNA levels were increased in the mutant. The concentration of copper was very low in the liver of the mutant, and on day 6 after birth the metallothionein mRNA was also reduced by about 50%. This reduction was not seen in copper-deficient 6-day-old pups, despite very low hepatic copper levels. This suggests that the lower hepatic MT-I mRNA in the day 6 brindled mouse was not simply due to the reduction in hepatic copper and also that hepatic copper is not regulating metallothionein gene expression the liver of neonatal mice. After day 12 hepatic MT-I mRNA levels were elevated in mutant and in copper deficient mice, both of which die at 14 to 16 days. These increases and the increase in brain MT-I mRNA in older mutant mice are likely to be caused by stress. Overall the results support the conclusions that the brindled mutation does not cause a constitutive activation of the metallothionein genes, and that the differences in metallothionein mRNA between mutant and normal are most probably secondary consequences of the mutation.

Topics: Animals; Blotting, Northern; Brain; Copper; Female; Gene Expression Regulation; Kidney; Liver; Male; Metal Metabolism, Inborn Errors; Metallothionein; Mice; Mice, Mutant Strains; Mutation; RNA, Messenger; Tyrosine Transaminase; Zinc

In certain pathological and experimental conditions associated with hepatic copper overload, an important portion of the excess metal is bound to a copper-thionein and sequestered in hepatocellular lysosomes. The localization can be demonstrated visually by using histochemical and immunocytochemical stains and by extraction of the Cu-protein from particulate fractions of liver homogenates. The livers of Bedlington terriers affected by an inherited defect resulting in the accumulation of large quantities of copper display hepatocellular lysosomes which appear as dense, insoluble, copper-rich granules. Purification and solubilization of the fraction containing these granules yields a copper-thionein with little zinc, which displays homology with other known metallothioneins. Although the primary genetic defect which underlies the pathogenesis of this form of hepatic copper overload is still unknown, circumstantial evidence suggests that sequestration of the protein by lysosomes may be temporarily cytoprotective.

Topics: Aging; Animals; Copper; Disease Models, Animal; Dogs; Hepatolenticular Degeneration; Liver; Lysosomes; Metal Metabolism, Inborn Errors; Metallothionein; Microscopy, Electron

The role of metallothionein (MT) was assessed in the copper-loading disease prevalent in Bedlington terriers. Fractionation of tissue supernatants over Sephadex G-75 showed that most of the additional cytosolic copper present in liver tissue of these dogs was bound to MT, and that substantially more MT-bound copper could be solubilized by detergent plus mercaptoethanol. Zinc contents were only slightly raised, although most of the extra zinc was associated with a 4000-Mr ligand. Ion-exchange chromatography revealed two isoproteins, MT1 and MT2, in all the dog liver samples examined. In Bedlington terrier liver, copper associated with both isoproteins was increased, although the increase for MT2 was greater than for MT1. The content of MT protein was also raised, although cell-free translations and RNA blots of total liver RNA showed that this increase was not associated with a rise in MT mRNA. The significance of these results to the mechanism of copper accumulation in the Bedlington terrier disorder is discussed.

Topics: Animals; Chromatography, Gel; Chromatography, Ion Exchange; Copper; Dog Diseases; Dogs; Liver; Metal Metabolism, Inborn Errors; Metallothionein; Protein Biosynthesis; RNA, Messenger; Subcellular Fractions; Zinc