Metallothionein In Rat Kidney Research Articles

Supplemental Dietary Cystine Elevates Kidney Metallothionein in Rats by a Mechanism Involving Altered Zinc Metabolism

Dietary sulfur-containing amino acids influence zinc and copper status. This study was conducted to investigate the relationship between the status of these elements and tissue metailothionein in rats fed diets supplemented with sulfur-containing amino acids. In a series of experiments, a diet containing 100 g casein/kg diet was unsupplemented or supplemented with L-cystine (3–50 g/kg diet) or L-methionine (3 or 30 g/kg diet). Kidney concentrations of zinc and copper in rats fed the diet supplemented with high levels of cystine (25 or 50 g/kg) were significantly higher than those in rats fed the unsupplemented diet. Kidney concentrations of metallothionein and metallothionein mRNA were also significantly higher in rats fed cystine-supplemented diets. There was a correlation (r = 0.838, P < 0.01) between the levels of zinc and metallothionein in kidney of rats fed the diets with different levels of cystine and zinc. However, in the rats fed the diets with different levels of cystine and copper, the correlation was not as strong (r = 0.587, P < 0.01). The changes in kidney metallothionein concentration due to the addition of 3 or 30 g/kg cystine were associated with parallel changes in serum zinc concentration and in apparent absorption of zinc, but not in serum copper concentration or apparent absorption of copper. Addition of 3 or 30 g methionine/kg diet to the diet did not affect kidney concentrations of metallothionein or zinc. These results indicate that supplementation of cystine to the diet can induce kidney metallothionein through a mechanism involving altered zinc metabolism.

Histochemical characterization of silver-induced metallothionein in rat kidney

Histochemical characterizations of Ag-induced metallothionein (MT) in the kidney of the rat have been reported. Ag, Cu and Zn contents increased in kidney and liver after Ag injection. In particular, the Cu content in kidneys increased dramatically after three injections of Ag. Sephadex G-75 elution profiles of the renal cytosol of rats injected with Ag revealed that the accumulated Cu in the kidney was bound to MT as were Ag and Zn. In addition, localization of Cu- and Ag-MT in the kidney was studied using autofluorescent signals, which are dependent on Cu- or Ag-thiol clusters, and immunohistochemistry. Although the MT induced by Ag was predominantly observed in the cortex of the kidney, some MT signals were also detected in the outer stripe of the outer medulla, as well as in the kidneys of LEC rats, an animal model of Wilson disease (a hereditary disorder of Cu metabolism). In these LEC rats, the Cu-MT also accumulated in the outer stripe of the outer medulla of the kidney. From these results, one possibility could explain that the Cu-MT detected in the outer stripe of the outer medulla in the kidney of Ag-injected rat was associated with the Cu transporter affected by Ag.

Effects of dietary zinc restriction on bismuth induction of rat kidney metallothionein

Bismuth-stimulated elevation of metallothionein levels is proposed to inhibit side effects of chemotherapy drugs such as cisplatin and adriamycin. In the present study, low zinc intake by rats limited bismuth-induced accumulation of renal metallothionein protein, and metallothionein-associated zinc and bismuth. In contrast, bismuth strongly elevated metallothionein mRNA in rats fed low zinc. Thus, bismuth does not appear to require zinc to stimulate high metallothionein mRNA accumulation, but seems to need this metal to accumulate metallothionein protein. Therefore, the efficacy of bismuth in restricting chemotherapy drug side effects in humans may depend on the zinc status of the people under treatment.

Time-dependent uptake and metallothionein-binding of gold, copper and zinc in the rat kidney

In rats, in which the whole body burden of Au decreases rapidly, but biphasically, maximum kidney concns are not attained until 10–15 days after a single intraperitoneal dose of either Au(I) or Au(III). The concn of metallothionein-bound Au and of total kidney Cu, which also increases after the administration of the Au compounds, however, reach maxima at 5 days. Between at least 6 and 24 hr after Au treatment, the increases in the concn of Au and Cu in the metallothionein fraction are highly correlated. Measurements on the kidneys of animals at early times (15 min-6 hr) after dosing with Au(III) indicate that the Zn content of the (endogenous) metallothionein is depressed during the first hour, shows a transient increase at 2 hr and then falls to a minimum at 6 hr. Subsequent (6–24 hr) changes in metallothionein-bound Zn parallel those of metallothionein-bound Au and Cu. It seems, therefore, that Au and Cu are incorporated simultaneously into rat kidney metallothionein and this incorporation may be mediated by an initial displacement of Zn. In rats exposed to five doses of Au(III) the half-times of total and metallothionein-bound Au in the kidneys are appreciably longer than those in animals given a single dose. In both groups, the concns of Cu and Zn in the renal metallothionein do not decrease in parallel with that of Au, but change roughly in proportion to their whole kidney concns. In consequence, the metal composition of the metallothionein fraction, which remains above the endogenous concn in the normal kidney throughout an experimental period of 90–140 days, alters considerably with time.

Effects of dietary mercury level and cadmium on rat tissue metallothionein: Mercury binding and influences on zinc

Feeding low levels of mercury in diets for rats results in its deposition with metallothionein (MT) in the kidney, but not in the liver. The addition of high levels of mercury to diets for rats caused the accumulation of mercury in kidney MT and to a much lesser extent in this low-molecular-weight protein in the liver. The accumulation of mercury in MT also caused zinc to accumulate in it. Treatment of rats with cadmium caused dietary mercury to accumulate in MT in the liver. Feeding stable mercury in the diet caused an increased uptake of labeled mercury in rat kidney MT, but in contrast, caused a decreased content in the liver MT. The mercury proteins from liver and kidney were purified and the amino acid analyses indicated that they are MT. Thus, MT binds low levels of mercury likely to be found in the environment in the kidney but not in the liver.

Induction of Kidney Metallothionein and Metallothionein Messenger RNA by Zinc and Cadmium

The influence of a 7.7-µmole (0.5-mg) dose of parenteral zinc on the synthesis of metallothionein in rat kidney was examined. The amount of zinc bound to metallothionein was maximal 9–15 hours after zinc administration. Pulse labeling with [35S]cystine showed the rate of renal metallothionein was stimulated to a maximum 6 hours after zinc administration and declined thereafter. Total RNA was extracted by the guanidine thiocyanate procedure from kidneys that had been flash frozen in liquid N2. Polyadenylated RNA (mRNA) was isolated by oligo (dT)-cellulose chromatography. The mRNA was translated in a wheat germ system and newly synthesized metallothionein was isolated by activated thiol-Sepharose 4B chromatography. Metallothionein mRNA activity nearly doubled after zinc administration and was closely correlated with the enhancement in synthetic rate of this protein in kidney. Actinomycin D administered prior to either zinc or cadmium completely blocked both the stimulation of metallothionein synthesis and mRNA activity found in kidney in response to these metals. The results suggest renal metallothionein is induced by zinc or cadmium through a mechanism that requires altered expression of the metallothionein gene(s).kidney metallothionein induction mRNA zinc cadmium protein synthesis

Decreased copper content in rat kidney metallothionein and its relation to acute cadmium nephropathy

Repeated s.c. injections of cadmium chloride into rats (3 mg Cd/kg body weight, 4 times a week) caused acute and transitory tubular necrosis after 2 to 3 weeks; recovery was observed after 4 weeks despite continued loading. Kidney copper decreased for the first 3 weeks and was slightly increased after 4 weeks. Distribution profiles of cadmium (Cd), zinc (Zn), copper (Cu) on an SW column revealed that elution profiles of kidney metallothionein changed from typical kidney with high copper content to typical liver metallothioneins with tubular necrosis and restoration.

The in vivo effects of maleate on the cation-distribution in rat kidney metallothionein sub-fractions after induction by cadmium and/or mercury

The metallothionein fractions, isolated by gel filtration from the kidneys of rats that have been dosed with Cd 2+, Hg 2+ or Cd 2+ followed by Hg 2+, yield very different elution profiles on ion-exchange chromatography. The metallothionein from Cd 2+-treated animals is resolved into the isomethallothioneins I and II and a minor, less negatively-charged species (B), which contains Cd 2+ and copper, but little Zn 2+. The corresponding fraction from the kidneys of rats dosed with Hg 2+ yields five components, all of which contain Hg 2+, Zn 2+ and Cu, but in different ratios. Three of these compounds correspond in their elution characteristics from DE-cellulose with the above-mentioned isometallothioneins I and II and fraction B. The last of these, which also is rich in Cu, is the major Hg 2+-binding component. The distribution of Hg 2+ and of other cations between these five sub-fractions, but not the number of sub-fractions, is altered by Cd 2+-pretreatment of the animals. Treatment of Cd 2+-dosed rats with sodium maleate has no significant effect on the distribution of cations (Cd 2+, Zn 2+ and copper) amongst the renal metallothionein subfractions. The same treatment, applied to animals dosed with either Hg 2+ only, or Cd 2+ followed by Hg 2+, causes the elimination of 70–75% of the Hg 2+ from the metallothionein fraction. Loss occurs from all subfractions, but is greatest in subfraction B, which also loses copper. Whilst it is possible that Hg 2+ may induce metallothionein and other metalloproteins in the kidney, Hg 2+ appears to bind to both isometallothioneins I and II, when these are induced by Cd 2+-pretreatment. The loss of Hg 2+, but not of Cd 2+, from these metalloproteins after treatment with sodium maleate may be related to differences in the relative binding affinities of the two cations for thionein and other cellular proteins.

Rat kidney metallothionein induced by injection of Cd-thionein: Changes of chromatographic properties with time and their relation to copper content and kidney dysfunction

Cadmium (Cd)-thionein was injected i.p. into adult rats to try to establish the relation between copper (Cu) content in the kidneys and its effect on the properties of metallothionein induced in the kidneys. Elution profiles of the re-synthesized kidney metallothionein changed with time after injection both on a Sephadex and on a gel permeation column (TSK GEL SW3000). The changes were correlated with Cu content in the kidneys caused by kidney dysfunction upon injection of Cd-thionein.

Chromatographic Properties of Metallothioneins on a Gel Permeation Column: Changes Induced by Replacement of Cadmium with Cuprous and Cupric Ions

Abstract In vitro experiments were conducted to find whether or not a similar elution profile to rat kidney metallothionein with high copper content was obtained on a gel permeation column by replacement of cadmium and/or zinc in rat liver metallothionein with copper. Stepwise replacement of cadmium in rat liver metallothionein with cuprous ion did not cause any shifts of retention times from those of the original proteins on a gel permeation column (SW 3000 column). In contrast to cuprous ion, stepwise replacement of cadmium with cupric ion induced shifts of retention times to larger values than the original ones for the two isometallothioneins on a SW column. Replacement of zinc in zinc-thionein with cupric ion but not with cuprous ion caused a retardation of elution volume on a Sephadex G-75 column. The decreases of cadmium peaks were accompanied by the increases of copper peaks in the case of replacement of cadmium in metallothionein with cuprous ion. Although stepwise decreases of cadmium peaks were ...

Fate of intraperitoneally injected liver metallothionein in rat kidney.

Isolated rat liver metallothionein was injected intraperitoneally into female rats to find whether or not the injected metallothionein was recovered from the kidneys with high copper content as in the case of rat kidney metallothionein induced by exposure to inorganic cadmium ion. The distribution patterns of cadmium and zinc among protein fractions in the kidney supernatants changed dramatically within one day after the injection. The changes were explained by the degradation and re-synthesis of the injected metallothionein in the kidneys. Copper was not found as a major metal in any metal-lothionein fractions obtained from the kidney supernatants. This is in marked contrast to cadmium ion-exposed rat kidney metallothionein. The relationships between the selective and profound toxicity of the injected metallothionein to the tubular lining cells and the changes of the chemical forms of cadmium were also discussed.

Copper in cadmium-exposed rat kidney metallothionein.

In vitro affinity of cupric ion to metallothionein was found to be stronger than cadmium and zinc ions. The result suggested the passive incorporation of copper into the metallothionein and the possibility of demasking of the masked cadmium toxicity as metallothionein. Copper contents of cadmium-exposed rat kidney metallothionein were analyzed along with cadmium and zinc. The copper in kidney metallothionein was always one of major metals along with zinc and cadmium. On the other hand, the copper in cadmium-exposed liver metallothionein was a minor metal.