|
Title
Ameliorative capacities of vitamins and monothiols post therapy
in the
restoration of methylmercury altered glutathione metabolism.
Author
ViJayalakshmi K; Sood PP
Address
Department of Biosciences' Saurashtra University' RaJkot' India.
Source
Cell Mol Biol (Noisy-le-grand), 40(2):211-24 1994 Mar
Abstract
The recovery of glutathione and its metabolising enzymes (glutathione
disulfide reductase' glutathione peroxidase' thiol transferase'
gamma-glutamyl transpeptidase and glutathione transferase) along
with
sulfhydryl groups and byproduct of lipid peroxidation (malondialdehyde)
in the brain' spinal cord' kidney and liver of mice' altered
during
methylmercury chloride (MMC) intoxication' is recorded in
post-therapeutic treatment with vitamins and monothiols. For
this
purpose ten groups of animals were intoxicated with 1 mg/kg MMC/day
for
7 days. Out of these' one group was sacrificed on 8th day and
one group
was kept without toxicant for another seven days before sacrificing
on
15th day. Study shows significant decrease of various biomolecules
of
glutathione metabolism during MMC application' which are further
decreased with increasing the duration on 15th day. The trend
is same
in all the tissues with few exceptions. However' malondialdehyde'
a
byproduct of lipid peroxidation' is increased with increasing
the
duration after intoxication. Study also shows a significant recovery
(in many cases a complete control level) of most of the components
with
one or the other chelator or with their combined therapy. Therefore'
it
is concluded from overall study that vitamins B complex and E'
GSH (or
its precursor NAHT) either alone or in combinations' are quite
suitable
for methylmercury post-therapy.
Title
Bidirectional membrane transport of intact glutathione in Hep
G2 cells.
Author
Sze G; Kaplowitz N; Ookhtens M; Lu SC
Address
Department of Medicine' University of Southern California School
of
Medicine' Los Angeles 90033.
Source
Am J Physiol, 265(6 Pt 1):G1128-34 1993 Dec
Abstract
Rat hepatocytes exhibit bidirectional carrier-mediated transport
of
reduced glutathione (GSH) across the plasma membrane. Transport
of GSH
has not been well characterized in human-derived cells. We examined
Hep
G2 cells as a possible human liver model for GSH homeostasis.
Hep G2
cell GSH averaged 25.9 +/- 1.4 nmol/10(6) cells. When Hep G2
cells were
incubated in buffer' no GSH appeared in the medium over 2 h.
However'
after pretreatment with acivicin to inhibit gamma-glutamyl
transpeptidase activity' GSH efflux was unmasked and measured
30 +/- 4
pmol x 10(6) cells-1 x min-1' which is comparable to rat hepatocytes.
GSH efflux was inhibited by sulfobromophthalein GSH adduct (BSP-GSH)
and cystathionine' agents that inhibit sinusoidal efflux in the
rat'
and was stimulated by adenosine 3`'5`-cyclic monophosphate-dependent
agents. GSH uptake was measured after cells were pretreated with
acivicin and buthionine sulfoximine to prevent breakdown of GSH
and
resynthesis of GSH from precursors' respectively. In the presence
of 4
microCi/ml of [35S GSH and 10 mM unlabeled GSH' GSH uptake was
linear
up to 45 min and did not require Na+ or Cl-. GSH uptake exhibited
saturability with a maximal velocity of 4.15 +/- 0.23 nmol.mg-1
x 30
min-1' a Michaelis constant of 2.36 +/- 0.26 mM' and two interactive
transport sites. BSP-GSH cis-inhibited GSH uptake in a dose-dependent
manner with an inhibitory constant of 0.46 +/- 0.05 mM. Inhibition
by
BSP-GSH (1 mM) of GSH uptake was through a single inhibitor site
and
was overcome at > 10 mM GSH' which is consistent with competitive
inhibition. Similar to the rat' 10 mM extracellular GSH
trans-stimulated GSH efflux. These findings may be important
in gaining
better insights into GSH homeostasis in human liver cells.
Title
glutathione content of the small intestine: regulation and function.
Author
Kelly FJ
Address
Department of Human Nutrition' University of Southampton.
Source
Br J Nutr, 69(2):589-96 1993 Mar
Abstract
In ad lib.-fed rats the epithelium of the small intestine' like
the
liver' contains large quantities of glutathione' 17.0 and 32.4
nmol/mg
protein respectively. Following 24 h food restriction the glutathione
content in both tissues fell 53 and 69% respectively. Unlike
the liver'
however' the glutathione content of the intestinal mucosa is
not
regulated to a diurnal rhythm' suggesting that the liver may
provide
glutathione or glutathione precursors to maintain intestinal
glutathione levels. Intestinal epithelial cell preparations obtained
from 24 h food-deprived rats had depleted glutathione stores
(50%) and
as a consequence were more susceptible to the oxidizing effects
of
cumene hydroperoxide. These results suggest that if glutathione
plays a
maJor role in the defence of the intestinal mucosa from ingested
toxins
then depletion of this defence during periods of food restriction
could
significantly increase the susceptibility of the individual to
toxins
present in the diet.
Title
Oral glutathione increases tissue glutathione in vivo.
Author
Aw TY; Wierzbicka G; Jones DP
Address
Department of Physiology' Louisiana State University Medical
Center'
Shreveport 71130.
Source
Chem Biol Interact, 80(1):89-97 1991
Abstract
Mice were given an oral dose of glutathione (GSH) (100 mg/kg)
and
concentrations of GSH were measured at 30' 45 and 60 min in blood
plasma and after 1 h in liver' kidney' heart' lung' brain' small
intestine and skin. In control mice' GSH concentrations in plasma
increased from 30 microM to 75 microM within 30 min of oral GSH
administration' consistent with a rapid flux of GSH from the
intestinal
lumen to plasma. Under these GSH-sufficient conditions' no increases
over control values were obtained in GSH concentrations in most
tissues
except lung over the same time course. Mice pretreated for 5
days with
the GSH synthesis inhibitor' L-buthionine-S'R-sulfoximine (BSO'
80
mumol/day) had substantially decreased tissue concentrations
of GSH.
Oral administration of GSH to these GSH-deficient animals gave
statistically significant increases in GSH concentrations in
kidney'
heart' lung' brain' small intestine and skin but not in the liver.
Administration of the equivalent amount of the constituent amino
acids'
glutamate' cysteine' and glycine' resulted in little change in
GSH
concentrations in all tissues in GSH-deficient animals. Thus'
the
results show that oral GSH can increase GSH concentrations in
several
tissues following GSH depletion' such as can occur in toxicological
and
pathological conditions in which GSH homeostasis is compromised.
Title
Cytoprotective effects of glycine and glutathione against hypoxic
injury to renal tubules.
Author
Weinberg JM; Davis JA; Abarzua M; Rajan T
Address
Department of Internal Medicine, Veterans Administration Medical
Center, Ann Arbor, Michigan.
Source
J Clin Invest, 80(5):1446-54 1987 Nov
Abstract
Roles for both the tripeptide, GSH, and individual amino acids
in
modifying the cellular response to oxygen deprivation-induced
injury
have been suggested by prior work in kidney and other tissues,
but the
precise interrelationships have not been clearly defined. We
have
studied the effects of GSH, its component amino acids, and related
compounds on the behavior of isolated renal proximal tubules
in a well
characterized model of hypoxic injury in vitro. GSH, the combination
of
cysteine, glutamate, and glycine and glycine alone, when present
in the
medium during 30 min hypoxia, a duration sufficient to produce
extensive irreversible injury in untreated tubules, were protective.
Significant effects were detected at 0.25 mM concentrations of
the
reagents, and protection was nearly complete at concentrations
of 1 mM
and above. glutamate and cysteine alone were not protective.
The
exogenous GSH added to the tubule suspensions was rapidly degraded
to
its component amino acids. Treatment of tubules with GSH or cysteine,
but not glycine, increased intracellular GSH levels. Oxidized
GSH was
protective. Serine, N-(2-mercaptopropionyl)-glycine, and a panel
of
agents known to modify injury produced by reactive oxygen metabolites
were without benefit. These observations identify a novel and
potent
action of glycine to modify the course of hypoxic renal tubular
cell
injury. This effect is independent of changes in cellular GSH
metabolism and appears to be unrelated to alterations of cell
thiols or
reactive oxygen metabolites. Further elucidation of its mechanism
may
provide insight into both the basic pathophysiology of oxygen
deprivation-induced cell injury and a practical way to ameliorate
it.
Title
glutathione content as an indicator for the presence of metabolic
pathways of amino acids in astroglial cultures.
Author
Dringen R; Hamprecht B
Address
Physiologisch-chemisches Institut der Universit at' T ubingen'
Germany.
Source
J Neurochem, 67(4):1375-82 1996 Oct
Abstract
The intracellular content of glutathione in astroglia-rich primary
cultures derived from the brains of newborn rats was measured
to be
32.1 +/- 5.4 nmol/mg of protein. During a 24-h incubation in
a minimal
medium lacking amino acids and glucose' the content of glutathione
in
these cultures was reduced to 52% of the original content. On
refeeding
of glucose' glutamate' glycine' and cysteine' glutathione was
resynthesized. A maximal content of glutathione was found 4 h
after
refeeding' exceeding the amount of glutathione of untreated cultures
by
72%. Maximal glutathione synthesis was observed only if glutamate'
cysteine' and glycine were present. If successively each one
of these
amino acids was made limiting for the synthesis of glutathione'
half-maximal contents of glutathione were found at 0.2 mM glutamate'
20
microM cysteine' or 10 microM glycine. Replacement of glutamate
or
glycine by other amino acids revealed the potential of astroglial
cells
to convert glutamine' aspartate' asparagine' proline' and ornithine
into glutamate' and serine into glycine. These results demonstrate
that
the concentration of intracellular glutathione can serve as an
indicator for the presence of metabolic pathways of amino acids
in
cultured cells.
Title
Effect of salicylates and phenobarbital on hepatic glutathione
in the
rat.
Author
Kaplowitz N; Kuhlenkamp J; Goldstein L; Reeve J
Source
J Pharmacol Exp Ther, 212(2):240-5 1980 Feb
Abstract
Phenobarbital and salicylates were shown to have opposite effects
on
hepatic glutathione. Phenobarbital increased glutathione concentration
by approximately 20 to 30%. This increase occurred within 48
hr and
could be attributed almost exclusively to an increase in bound
glutathione. No changes in ATP' substrate amino acids for glutathione
synthesis or the level of gamma-glutamylcysteine synthetase'
the rate
limiting enzymatic step in glutathione synthesis' were found
with
phenobarbital. Phenobarbital' which induces hepatic proteins
that bind
glutathione' increased bound glutathione but did not affect unbound
glutathione. Therefore' the concentration of the latter probably
regulates glutathione synthesis. Salicylates (aspirin and sodium
salicylate) were found to deplete hepatic glutathione in both
saline-
and phenobarbital-treated rats. Maximum depletion (approximately
40%)
was seen 4 to 6 hr after salicylate administration and returned
toward
the control level by 12 hr. The salicylate effect was not related
to a
change in gamma-glutamylcysteine synthetase' gamma-glutamyl
transpeptidase or the concentrations of free hepatic glycine'
glutamate' cysteine and methionine. An increase in concentration
of
glutathione both in vivo in plasma from salicylate-treated rats
and in
vitro in buffer from the incubation of liver slices with salicylate
suggests that glutathione leakage from hepatocytes is an important
factor in salicylate-induced hepatic glutathione depletion.
Title
glutathione turnover in cultured astrocytes: studies with [15N
glutamate.
Author
Yudkoff M; Pleasure D; Cregar L; Lin ZP; Nissim I; Stern J; Nissim
I
Address
Division of Metabolism' University of Pennsylvania School of
Medicine'
Philadelphia.
Source
J Neurochem, 55(1):137-45 1990 Jul
Abstract
The incorporation of [15N glutamic acid into glutathione was
studied in
primary cultures of astrocytes. Turnover of the intracellular
glutathione pool was rapid' attaining a steady state value of
30.0
atom% excess in 180 min. The intracellular glutathione concentration
was high (20-40 nmol/mg protein) and the tripeptide was released
rapidly into the incubation medium. Although labeling of glutathione
(atom% excess) with [15N glutamate occurred rapidly' little
accumulation of 15N in glutathione was noted during the incubation
compared with 15N in aspartate' glutamine' and alanine. glutathione
turnover was stimulated by incubating the astrocytes with
diethylmaleate' an electrophile that caused a partial depletion
of the
glutathione pool(s). Diethylmaleate treatment also was associated
with
significant reductions of intraastrocytic glutamate' glycine'
and
cysteine' i.e.' the constituents of glutathione. glutathione
synthesis
could be stimulated by supplementing the steady-state incubation
medium
with 0.05 mM L-cysteine' such treatment again partially depleting
intraastrocytic glutamate and causing significant reductions
of 15N
labeling of both alanine and glutamine' suggesting that glutamate
had
been diverted from the synthesis of these amino acids and toward
the
formation of glutathione. The current study underscores both
the
intensity of glutathione turnover in astrocytes and the relationship
of
this turnover to the metabolism of glutamate and other amino
acids.
Title
The biosynthesis of glutathione in human erythrocytes (author's
transl)
Author
Heinle H; Sawatzki G; Wendel A
Source
Hoppe Seylers Z Physiol Chem, 357(11):1451-8 1976 Nov
Abstract
The concentrations of glutathione precursors in human erythrocytes
were
investigated. 300muM glutamate, 375 muM glycine, and 10muM cysteine
were found by automated amino acid analysis. The concentration
of
2-aminobutyrate, the precursor of ophthalmic acid, was 15muM.
The
influence of the activities of endogenous or added glutamyl-cysteine
synthetase and glutathione synthetase on the rate of glutathione
biosynthesis was measured in membrane-free hemolysates under
physiological conditions. The results show that the rate of the
overall
biosynthesis mainly depends on the formation of the dipeptide
glutamyl-cysteine. The effect of glutathione precursor concentrations
on the synthesis of the tripeptide was investigated at constant
(endogenous) activities of the synthesizing enzymes. The rate
was not
enhanced by addition of glutamate and/or glycine unless cysteine
or
glutamyl-cysteine was also added. It is concluded that the
concentration of cysteine limits the actual rate of the
glutamyl-cysteine-synthetase reaction in vivo. No cysteine or
bis(glutamyl)cystine was detected in human hemolysate; however,
these
disulfides were converted to glutathione. This indicates that
erythrocytes have an appropriate system for their reduction,
since the
disulfides themselves are not substrates for the
glutathione-synthesizing enzymes. Studies with intact human red
cells
indicate that the uptake of cysteine is the rate-determining
step in
the biosynthesis of glutathione.
Title
Nutritional role of chromium.
Author
Anderson RA
Source
Sci Total Environ, 17(1):13-29 1981 Jan
Abstract
Chromium is an essential trace element required for normal carbohydrate
metabolism. The biological function of chromium is closely associated
with that of insulin and most chromium-stimulated reactions are
also
insulin dependent. Proper chromium nutrition leads to a decreased
requirement for insulin and also an improved blood lipid profile.
Most
fresh foods and minimally processed foods are good sources of
dietary
chromium. Inorganic chromium does not potentiate insulin action
and
must be converted to an organic biologically active form. An
organic
form of chromium capable of potentiating insulin has been isolated
from
brewer`s yeast and was shown to contain: Cr' nicotinic acid and
a
combination of amino acids. Synthetic insulin potentiating organic
chromium complexes containing chromium' nicotinic acid' glycine'
cysteine' and glutamic acid or chromium' nicotinic acid and glutathione
have been prepared. These complexes have not been purified to
homogeneity since they dissociate during purification. Suitable
analytical bioassays are available to measure total chromium
and the
organic biologically-active forms of chromium' respectively.
Title
Different preferences in the utilization of amino acids for glutathione
synthesis in cultured neurons and astroglial cells derived from
rat
brain.
Author
Kranich O; Hamprecht B; Dringen R
Address
Physiologisch-chemisches Institut der Universit at' T ubingen'
Germany.
Source
Neurosci Lett, 219(3):211-4 1996 Nov 29
Abstract
The intracellular contents of glutathione in neuron-rich and
astroglia-rich primary cultures derived from the brains of embryonal
and newborn rats were found to be 23.1 +/- 3.0 and 31.2 +/- 6.5
nmol/mg
of protein' respectively. Deprivation of amino acids for 4 h
reduced
the level of glutathione in neuron-rich cultures by 24%. glutathione
was resynthesized on refeeding of cysteine' glutamine' and glycine.
A
maximal content of glutathione was found 4 h after refeeding'
exceeding
that of untreated neuron-rich cultures by 84%. Replacement of
cysteine
by cystine or glutamine by glutamate during the 4 h refeeding
period
resulted in a lower intracellular amount of glutathione. An increase
in
the glutathione level of neuron-rich cultures by 76% was found
if the
culture medium was supplemented with 250 microM cysteine. However'
no
such increase occurred if cystine was used instead. In contrast
to
neuron-rich cultures' astroglia-rich primary cultures restored
a
maximal content of glutathione if glutamate and cystine were
refed
after amino acid deprivation. These results demonstrate that
cysteine
is the limiting compound in the culture medium for glutathione
synthesis in neuron-rich cultures and that astroglial cells and
neurons
in culture have different preferences for uptake and utilization
of
amino acids for glutathione synthesis.
Title
Properties of glutathione peroxidase isolated from human plasma.
Author
Broderick DJ; Deagen JT; Whanger PD
Address
Department of Agricultural Chemistry, Oregon State University,
Corvallis 97331-6502.
Source
J Inorg Biochem, 30(4):299-308 1987 Aug
Abstract
Human plasma glutathione peroxidase (GPx) was purified to homogeneity
by ammonium sulfate fractionation, gel filtration on Sephadex
G-150,
chromatography on DEAE Sephacel, chromatofocusing with polybuffer,
and
gel filtration with Sephadex G-75. This isolation resulted in
about
5,400-fold purification of the enzyme with a 32% yield in enzyme
activity. The final preparation had a specific activity of about
28
units (mmoles NADPH oxidized) per milligram of protein. Determination
of selenium on the purified enzyme revealed a content of 3.8
g atoms
per mole GPx. Gel electrophoresis using SDS with standard proteins
revealed a molecular weight of about 23,000 for the subunits,
which
would indicate a molecular weight of about 92,000 for the native
enzyme. Amino acid analyses of the purified GPx indicated aspartate,
glutamate, proline, glycine, alanine, and leucine as the predominant
amino acids and cysteine, methionine, tryptophan, and histidine
as the
minor amino acids.
Title
Improved function with amino acids in the isolated perfused kidney.
Author
Epstein FH; Brosnan JT; Tange JD; Ross BD
Source
Am J Physiol, 243(3):F284-92 1982 Sep
Abstract
When isolated rat kidneys are perfused with glucose as the only
substrate' there is a progressive diminution in glomerular filtration
rate and fractional reabsorption of sodium. This is most marked
after 1
h. Renal glutathione content rapidly falls and is less than 30%
of
control levels after 1 h. Renal concentrating ability is markedly
impaired and structural lesions are consistently observed in
cells
lining the thick ascending limb of Henle`s loop. Addition of
20
physiologic amino acids including cysteine to the perfusate prevents
the fall in renal glutathione' prevents the anatomical damage
to
ascending limb cells' permits GFR and fractional sodium reabsorption
to
remain high and close to their initial levels for as long as
4 h' and
improves renal concentrating capacity. If amino acid supplementation
is
limited to three precursors of glutathione--cysteine' glycine'
and
glutamic acid--renal glutathione content is preserved and concentrating
ability is improved' but GFR and fractional sodium reabsorption
are not
maintained as well as with comprehensive amino acid supplements.
The
results suggest that amino acid deficiency and glutathione depletion
may contribute to disturbances in renal structure and function.
Title
Skeletal muscle glutathione after surgical trauma.
Author
Luo JL; Hammarqvist F; Andersson K; Wernerman J
Address
Anaesthesiological Metabolism Unit' Clinical Research Centre'
Karolinska Institute' Stockholm' Sweden.
Source
Ann Surg, 223(4):420-7 1996 Apr
Abstract
OBJECTIVE: The authors investigate the effect of surgical trauma
on
skeletal muscle concentrations of glutathione in patients undergoing
selective abdominal surgery. SUMMARY BACKGROUND DATA: The posttraumatic
state is accompanied by characteristic changes in the pattern
of free
amino acids and a decline of protein synthesis in human skeletal
muscle. glutathione has multiple metabolic functions that are
involved
in cellular homeostasis. It is unknown how surgical trauma affects
the
glutathione metabolism of skeletal muscle in surgical patients.
METHODS: Eight patients undergoing elective abdominal surgery
were
investigated. Percutaneous muscle biopsies and blood samples
were taken
before operation and at 6' 24' and 48 hours after operation.
The
concentrations of glutathione were determined in muscle tissue'
plasma'
and whole blood' as well as the concentrations of the related
amino
acids in muscle and plasma. RESULTS: In skeletal muscle' the
levels of
both reduced and total glutathione decreased by 40% (p<0.01)
at 24
hours and remained low at 48 hours after operation compared with
the
preoperative values. The glutathione concentration in plasma
was 20%
lower after operation compared with the concentration before
operation
(p<0.05). There were no changes at the whole blood levels
of
glutathione. Tissue glutamate and glutamine decreased significantly
after operation (p<0.001)' whereas intracellular cysteine
and glycine
remained unchanged. CONCLUSIONS: Skeletal muscle glutathione
deficiency
occurs after surgical trauma. This may lead to an increase in
the
susceptibility to intracellular oxidative injury. |
|
Return to Main Page
