Exogenous glutathione decreases cellular cadmium uptake and toxicity.
Department of Pharmacology and Toxicology' University of North
Dakota School of Medicine' Grand Forks 58203.
Drug Metab Dispos, 20(5):714-8 1992 Sep-Oct
The effect of intracellular glutathione (GSH) on cadmium metabolism
and toxicity has been extensively investigated. However' little
is known regarding the effect of extracellular GSH on cellular
cadmium responses. Therefore' this study was conducted to investigate
the effect of exogenously added GSH on cadmium toxicity in normal
rat kidney fibroblasts (NRK-49F). Exponentially growing NRK-49F
cells were arrested by serum deprivation and then stimulated
with epidermal growth factor (EGF). CdCl2' at concentrations
that range from 0.25 to 2 microM' was found to inhibit' in a
dose-dependent fashion' the EGF-induced DNA synthesis (as Judged
by [3H thymidine incorporation) in the cells. A long-term survival
assay revealed that CdCl2 above 1 microM was toxic to the cells.
Exogenous GSH had a dose-dependent antagonistic effect on cadmium
inhibition of EGF-induced DNA synthesis' and 1 mM GSH was found
to block completely cadmium inhibition of both EGF-induced DNA
synthesis and cell survival. Exogenously added GSH did not increase
intracellular GSH levels but decreased cadmium accumulation by
the cells. This decrease was primarily caused by a reduced cadmium
uptake. Further studies indicated that exogenous GSH would form
a complex with cadmium outside of the cells preventing cellular
cadmium uptake. This may explain the mechanism of action of the
exogenous GSH in cytoprotection against cadmium. The results
also suggested a practical potential for GSH as a cadmium chelator.
If GSH were coadministered with a cadmium mobilizer and a gamma-glutamyl
transpeptidase inhibitor' it could enhance cadmium excretion
from the body.
Effects of a hepato-protective agent and a hepato-secreting chelator
on cadmium-induced nephrotoxicity in Syrian hamsters.
Shibasaki T; Matsumoto H; Gomi H; Ohno I; Ishimoto F; Sakai O
Second Department of Internal Medicine' The Jikei University
School of Medicine' Nishi-Shimbashi' Minato-ku' Tokyo 105' Japan.
Biol Trace Elem Res, 52(1):1-9 1996 Apr
cadmium (Cd)-induced nephropathy in male Syrian hamsters was
treated with D/L-penicillamine (D/L-p) or neomynophagen C (NMC).
The subcutaneous inJection of CdCl(2)' 3 mg/kg' three times a
week led to marked renal damage' ie.' increased proteinuria and
the excretion of urinary N-acetyl-beta-D-glucosaminidase (NAG)
as compared with the saline-inJected controls. Cd-treated hamsters
that were inJected intraperitoneally with D/L-p' 0.1 mg/kg' five
times a week' showed less renal damage' including a reduction
in urinary protein from 3.60 + or - 0.42 to 1.77 + or - 0.7 mg/d.
NMC-treated hamsters showed a reduced excretion of NAG (from
1.47 +/ - 0.34 to 0.91 + or - 0.68 u/d). The concentration of
Cd in renal cortical tissue was reduced slightly (from 2.78 +
or - 0.08 to 2.34 + or - 0.3 mg/g.prot) by NMC treatment' but
not by D/L-p. The elevated malondialdehyde (MDA) in renal cortical
tissue was unaffected by administering D/L-p or NMC. The concentration
of glutathione (CSH) in the renal cortex was not elevated after
administering Cd' but the ratio of the reduced to the oxidized
GSH was elevated. The Cd induced liver dysfunction' as compared
with untreated controls. The dysfunction was improved slightly
by NMC administration' but not by that of D/L-p. Changes in renal
morphology induced by Cd involving marked degeneration and necrosis
of tubules as shown by light microscopy' were unaffected by treatment
with D/L-p or NMC. We thus demonstrated the efficacy of D/L-p
of NMC in treating the nephropathy induced by Cd in hamsters.
The mechanism of therapeutic effect is not known.
A comparative study of the influence of vicinal dithiols and
a dithiocarbamate on the biliary excretion of cadmium in rat.
Jones MM; Cherian MG; Singh PK; Basinger MA; Jones SG
Department of Chemistry' Vanderbilt University' Nashville' Tennessee
Toxicol Appl Pharmacol, 110(2):241-50 1991 Sep 1
The effect of two vicinal dithiols' 2'3-dimercaptopropan-1-ol
(BAL) and N-(2'3-dimercaptopropyl)phthalamidic acid (DMPA)' and
a dithiocarbamate' sodium N-(4-methoxybenzyl)-D-glucamine dithiocarbamate
(MeOBGDTC)' on the biliary excretion of cadmium was examined
in rats. Tissue cadmium levels were also determined following
the measurements of biliary excretion of cadmium. At 30 min after
the inJection of CdCl2.2.5H2O (1 mg/kg' iv) each rat was given
400 mumol/kg ip of one of the compounds' BAL' DMPA or MeOBGDTC.
While all the compounds increased the biliary excretion of cadmium'
the most effective was MeOBGDTC' whose administration resulted
in a 580% increase in biliary cadmium content. The effectiveness
of the MeOBGDTC may be due to the presence of both nonpolar and
nonionizing polar groups attached to nitrogen. MeOBGDTC was able
to mobilize cadmium to the bile even after the occurrence of
the synthesis of metallothionein and the incorporation of the
cadmium into it. An attempt was also made to determine the chemical
nature of the Cd-MeOBGDTC complex present in the bile by comparing
a newly synthesized authentic sample of Cd(MeOBGDTC)2 complex
with the hot dioxane extract of the freeze-dried bile samples
using thin-layer chromatography and proton NMR. The results suggested
that cadmium excreted in the bile in part' is complexed to MeOBGDTC
Nuclear magnetic resonance studies of the solution chemistry
of metal complexes. 26. Mixed ligand complexes of cadmium' nitrilotriacetic
acid' glutathione' and related ligands.
Kadima W; Rabenstein DL
Department of Chemistry' University of Alberta' Edmonton' Canada.
J Inorg Biochem, 38(4):277-88 1990 Apr
The complexation of glutathione and related ligands by the nitrilotriacetic
acid complex of Cd2+ (Cd(NTA)-) has been investigated by 1H NMR
as a model for the coordination chemistry of Cd2+ and GSH in
biological systems. Related ligands included glycine' glutamic
acid' cysteine' N-acetylcysteine' penicillamine' N-acetylpenicillamine'
mercaptosuccinic acid' and the S-methyl derivative of glutathione.
The nature of the complexes formed was deduced from 1H NMR spectra
of Cd(NTA)- and the ligands. Mixed ligand complexes (Cd(NTA)L)
and single ligand complexes (CdLx) are formed with the thiol
ligands' whereas only mixed ligand complexes form with glycine'
glutamic acid and S-methylglutathione. Formation constants of
the mixed and the single ligand complexes were determined from
NMR data. The results indicate that formation constants for binding
of a thiolate donor group by Cd2+' either as the free ion or
in a coordinately unsaturated complex' are in the range 10(5)-10(6).
Comparative investigations on the effects of acute intraperitoneal
cadmium, chromium, and mercury exposure on the kidney.
Bomhard E; Maruhn D; Vogel O
Uremia Invest, 9(2):131-6 1985-86
Urinary excretion of lactate dehydrogenase (LDH), glutathione-S-transferase
(GST), leucine arylamidase (LAS), gamma-glutamyltransferase (GGT),
beta-galactosidase (GAL), beta-N-acetyl-D-glucosaminidase (NAG),
sodium, and glucose were determined in female Sprague-Dawley
rats the subsequent three days after intraperitoneal treatment
with single doses of 4.5 mg CdCl2 X 1H2O/kg, 20 mg Na2CrO4/kg,
and 0.75 mg HgCl2/kg body weight. Although the pathological effects
were localized within the same part of the nephron (i.e., the
proximal tubule), there were marked differences with regard to
the extent and time course of the parameters affected. Treatment
with cadmium resulted essentially in a marked decline in sodium
and glucose excretion. The administration of chromate led to
a slightly to moderately elevated excretion of the enzyme activities
measured with the cytosolic LDH as the most increased enzyme
(ca. 500% of controls on Day 3 postadministration). Median glucose
excretion was unaffected whereas sodium excretion was transiently
reduced. The maximum of enzyme excretion after HgCl2 was essentially
the same on the first day postadministration and the amount of
enzyme activity in urine up to 20 times higher compared to that
after chromium. Sodium excretion was below that of controls on
Days 2 and 3, whereas glucose excretion was markedly elevated
(up to 8000% of controls). The results indicate that it is possible
to discriminate with the use of selected urinary enzymes, substrates,
and electrolytes various kinds of nephrotoxic actions not only
in different but also within the same part of the nephron.
Protective effects of GSH' vitamin E' and selenium on lipid peroxidation
in cadmium-fed rats.
Rana SV; Verma S
Department of Zoology' Ch. Charan Singh University' Meerut' India.
Biol Trace Elem Res, 51(2):161-8 1996 Feb
Increased intake of Cd results in its retention and in peroxidative
damage in soft tissues. Coadministration of antioxidants' viz.'
glutathione (GSH)' alpha-tocopherol' and Se' restricted the uptake
and distribution of Cd in liver and kidney of rats. Moreover'
no rise in malondialdehyde was recorded. Although possible antioxidative
mechanisms manifested by GSH' alpha-tocopherol' and Se have been
discussed' it is hypothesized that GSH functions as a Cd chelator.
glutathione yielded favorable effects in comparison to Se and
Effect of arsenicals on biliary excretion of endogenous glutathione
and xenobiotics with glutathione-dependent hepatobiliary transport.
Gyurasics A; Varga F; Gregus Z
Department of Pharmacology' University Medical School of P]ecs'
Biochem Pharmacol, 41(6-7):937-44 1991 Mar 15-Apr 1
Sodium arsenite (25-100 mumol/kg' i.v.) and arsenate (75-300
mumol/kg' i.v.) inJected into anaesthetized rats increased the
biliary excretion of endogenous non-protein thiols (NPSH) in
a dose-dependent fashion up to 24- and 31-fold' respectively.
Simultaneously with NPSH' glutathione (GS) excretion was increased
to a similar extent suggesting that the increment in biliary
thiol output originated from enhanced hepatobiliary transport
of GS. After administration of labelled arsenicals' biliary excretion
of 74As and NPSH followed similar time-courses. Biliary excretion
of 74As was more efficient after arsenite than arsenate administration
corresponding to the greater potency of arsenite compared to
arsenate to increase biliary output of NPSH. Coadministered sulfobromophthalein
(BSP) inhibited the biliary excretion of 74As and prevented the
arsenical-induced increase in biliary NPSH. Thus' hepatobiliary
transport of arsenic apparently proceeds coordinately with that
of GS. However' excretion of each molecule of arsenic compound
generates transport of several molecules of GS. Though mercuric'
methylmercuric' cadmium and zinc ions are thought to be excreted
into bile as complexes with GS' the marked arsenical-induced
increase in GS excretion only doubled the biliary excretion of
inorganic mercury and hardly influenced the transport of other
metals into bile. This finding suggests that arsenicals markedly
enhance biliary excretion of GS with a free thiol group but barely
or not at all that of GS with a thiol group blocked by a firmly
bound metal ion. Both arsenicals diminished the biliary excretion
of BSP-glutathione conJugate after BSP administration presumably
because they impaired conJugation of BSP with GSH due to decreased
GS availability. It is assumed that arsenite' and arsenate after
reduction to arsenite' forms an unstable complex with GS that
is efficiently transported into bile resulting in increased biliary
output of GS. It is demonstrated that arsenite-induced perturbation
of hepatobiliary disposition of endogenous GS differentially
affects biliary excretion of xenobiotics with GS-dependent hepatobiliary
Studies on the efficacy of lipoate and dihydrolipoate in the
alteration of cadmium2+ toxicity in isolated hepatocytes.
M uller L; Menzel H
Institute of Toxicology' University of D usseldorf' F.R.G.
Biochim Biophys Acta, 1052(3):386-91 1990 May 22
Lipoate (thioctic acid) is presently used in therapy of a variety
of diseases such as liver and neurological disorders. However'
nothing is known about the efficacy of lipoate and its reduced
form dihydrolipoate in acute cadmium (Cd2+) toxicity which involves
severe liver disturbances. Therefore' we investigated the effects
of these redox compounds on Cd2(+)-induced inJuries in isolated
rat hepatocytes. The cells were coincubated with 150 microM Cd2+
and either 1.5-6.0 mM lipoate or 17-89 microM dihydrolipoate
for up to 90 min and Cd2+ uptake as well as viability criteria
were monitored. Both exposure regimens diminished Cd2+ uptake
in correspondence to time and concentration. They also ameliorated
Cd2(+)-induced cell deterioration as reflected by the decrease
in Cd2(+)-induced membrane damage (leakage of aspartate aminotransferase)'
by the lessening of the Cd2(+)-stimulated lipid peroxidation
(TBA-reactants) and by the increase in Cd2(+)-depleted cellular
glutathione (GSH + 2 GSSG). Half-maximal protection was achieved
at molar ratios of 9.9 to 19 (lipoate vs. Cd2+) and 0.25 to 0.74
(dihydrolipoate vs. Cd2+)' indicating a 19.5 to 50.6 lower protective
efficacy of lipoate as compared to dihydrolipoate. Lipoate induced
an increase in extracellular acid-soluble thiols different from
glutathione. It is suggested that dihydrolipoate primarily protects
cells by extracellular chelation of Cd2+' whereas intracellular
reduction of lipoate to the dihydro-compound followed by complexation
of both intra- and extracellular Cd2+ contributes to the amelioration
provided by lipoate.
Influence of selenium supplement on cadmium metabolism in human
Chung Kuo I Hsueh Ko Hsueh Yuan Hsueh Pao, 11(3):185-9 1989 Jun
38 subjects were randomly divided into 2 groups of 19 each. Group
1 consumed a selenium supplement (150 micrograms/d X 21) and
Group 2 received only placebo(glucose). After supplementation,
blood Se levels and plasma GSH-Px activities in Group 1 increased
from 76 to 100 ng/ml (P less than 0.05) and 0.082 to 0.122 e.u./ml
(P less than 0.01) respectively. All measured Se, GSH-Px values
in Group 2, and high concentrations of lipid peroxides (greater
than 4 nmol/ml as malonaldehyde) in both groups remained approximately
the same. Se supplementation resulted in a marked decrease of
RBC cadmium (Cd) from 32.3 to 25.4 micrograms/g Hb (P less than
0.001). Urinary and fecal Cd in 5 subjects of each group were
analyzed every 4 days, and the results demonstrated that Cd was
mainly excreted in feces after Se supplementation. One week after
discontinuing of Se treatment, Cd content in urine and feces
decreased to control levels. Theoretical evidence for chemoprevention
of lung cancer with Se in this area was thus provided.
glutathione transferases in the urine: sensitive methods for
detection of kidney damage induced by nephrotoxic agents in humans.
Sundberg A; Appelkvist EL; Dallner G; Nilsson R
Clinical Research Center' Karolinska Institute' Huddinge Hospital'
Environ Health Perspect, 102 Suppl 3():293-6 1994 Sep
With the aid of immunohistochemical methods the localization
of the various isoenzymes of glutathione S-transferase was investigated.
The alpha isoenzyme was present solely in the proximal tubular
cells of the human kidney' while the pi form was restricted to
the distal convoluted tubules' the thin loop of Henle' and the
collecting ducts. Damage to the epithelial cell membranes results
in the increased excretion of these enzymes with the urine. The
alpha and pi isoenzymes have been isolated in a highly purified
form and used for the production of polyclonal antisera. Subsequently'
radioimmunological and ELISA techniques were developed for quantitation
of these proteins in the urine; the methods exhibited a high
specificity and were sufficiently sensitive to determine nanogram
quantities or less. Disease affecting tubular function' cyclosporine
A treatment' administration of nephrotoxic antibiotics' and exposure
to cadmium all resulted in characteristic changes in the pattern
of the glutathione transferase isoenzymes present in urine. Such
effects were seen also in patients who had previously been exposed
to nephrotoxic agents' but in whom conventional tests for kidney
function were apparently normal. Thus' it appears that radioimmunologic
or immunochemical quantitation of alpha and pi forms of the enzyme
can be used as sensitive and relatively simple markers for the
early detection of toxic effects with respect to the renal tubuli.
Role of metallothionein in metal detoxification and metal tolerance
in protein calorie malnutrition and calcium deficient monkeys
Nath R; Paliwal VK; Prasad R; Kambadur R
Department of Biochemistry, Postgraduate Institute of Medical
Education and Research, Chandigarh, India.
EXS, 52():631-8 1987
A monkey model has been set up for protein calorie malnutrition
and calcium deficiency. Oral exposure of 5ppm Cd/kg body wt./day
for 24 weeks led to increased excretion of Cd, metallothionein
(MT) and zinc. Rehabilitation of PCM monkeys for one year resulted
in gradual reduction and finally complete disappearance of urinary
metallothionein. During Cd exposure, the accumulation of Cd and
induction of MT was significantly higher in liver, kidney and
intestine. MT was also induced in heart, lung and testis of Cd
exposed PCM and calcium deficient monkeys. Metallothionein from
liver has been resolved into three isoforms, viz MTa, MTb and
MTc on DEAE-Sephadex A 25 ion exchange column. MTc is the major
isoform in Cd-treated, normal and protein calorie malnourished
monkeys whereas MTb is the major isoprotein in the cadmium treated
calcium deficient monkeys. The iso-metallothioneins varied in
their metal composition in the nutritional stress conditions
and showed different capacities to reactivate apo-enzymes viz.
alkaline phosphatase, ceruloplasmin, superoxide dismutase and
glutathione peroxidase. Thus, metallothionein plays a key role
in metal metabolism during cadmium toxicity under nutritional
Toxic heavy metal ions activate the heme-regulated eukaryotic
initiation factor-2 alpha kinase by inhibiting the capacity of
hemin-supplemented reticulocyte lysates to reduce disulfide bonds.
Matts RL; Schatz JR; Hurst R; Kagen R
Department of Biochemistry' Oklahoma State University' Stillwater
J Biol Chem, 266(19):12695-702 1991 Jul 5
Addition of toxic heavy metal ions (Cd2+' Hg2+' and Pb2+) to
hemin-supplemented rabbit reticulocyte lysate brings about the
activation of the heme-regulated eukaryotic initiation factor
2 alpha kinase (HRI) and the inhibition of protein chain initiation.
In this report we examined the effects of monothiol and dithiol
compounds' metal ion-chelating agents' and metallothioneins (MT)
on metal ion-induced inhibition of protein synthesis. The dithiol
compounds dithiothreitol and 2'3-dimercaptopropane sulfonic acid
prevented and relieved the inhibition of protein synthesis caused
by Cd2+ and Hg2+ in hemin-supplemented lysates' but the monothiol
compounds 2-mercaptoethanol' cysteamine' D-(-)penicillamine'
and glutathione had no effect. The inhibition of protein synthesis
caused by Cd2+ was reversed by the addition of excess EDTA but
not by the addition of excess nitrilotriacetic acid. Toxic heavy
metal ions inhibited the capacity of hemin-supplemented lysate
to reduce disulfide bonds. Addition of excess EDTA to Cd(2+)-inhibited
lysates restored the capacity of the lysate to reduce disulfide
bonds and inhibited the phosphorylation of eukaryotic initiation
factor eIF-2. MTs and their apoproteins (apoMTs) inhibited the
activation of HRI and protected protein synthesis from inhibition
by Cd2+' Hg2+' and Pb2+. Addition of apoMTs to heavy metal ion-inhibited
lysates restored the capacity of lysates to reduce disulfide
bonds. The restoration of the lysate`s thioredoxin/thioredoxin
reductase activity was accompanied by the inactivation of HRI
and the resumption of protein synthesis' indicating that apoMTs
can "detoxify metal ions already bound to proteins. Several
observations presented in this report suggest that the binding
of metal ions to the alpha-domain of MT is responsible for the
ability of MT to sequester bound metal in a non-toxic form. Addition
of glucose 6-phosphate or NADPH had no effect on protein synthesis
in metal ion-inhibited lysates' and NADPH concentrations in Cd(2+)-inhibited
and hemin-supplemented control lysates were equivalent. The data
suggest that the metal ions cause the inhibition of protein synthesis
by binding to vicinal sulfhydryl groups present in some critical
protein(s)' possibly the dithiols present in the active site
of thioredoxin and (or) thioredoxin reductase' which leads to
the activation of HRI.