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Title
Hepatic glutathione determination after ethanol administration
in rat:
evidence of the first-pass metabolism of ethanol.
Author
Battiston L; Moretti M; Tulissi P; Micheli L; Marchi P; Mazzoran
L;
Lunazzi G; Pozzato G
Address
Centro Studi Fegato' University of Trieste' Italy.
Source
Life Sci, 56(4):241-8 1995
Abstract
As a fraction of ingested ethanol is metabolized by gastric mucosa'
different amounts of alcohol should reach the liver when the
same dose
is administered by oral or intravenous route. Therefore' we
investigated the time-course of hepatic reduced glutathione (GSH)
concentrations after intra-peritoneal or intra-gastric load of
the same
amount of ethanol in the rat. The test was also performed in
fasted and
Cimetidine-treated rats. The oral ethanol administration was
followed
by a less pronounced decrease and by a quicker recovery of hepatic
content of GSH than after intraperitoneal route. In the fasted
rat'
basal hepatic GSH significantly decreased; after alcohol administration
the decrease of hepatic GSH was more severe and prolonged than
in the
fed rat. Cimetidine was shown to be a potent inhibitor of gastric
ADH.
Pre-treatment with Cimetidine did not change the basal levels
of
hepatic GSH' but after oral ethanol load' the decrease of the
hepatic
GSH content was significantly (p < 0.005) more pronounced
than in
controls. This study demonstrates the beneficial effects of gastric
ethanol metabolism on the liver. The reduced gastric ethanol
metabolism' induced by fasting or by Cimetidine resulted in a
decreased
content and delayed recovery of liver GSH content.
Title
Mitochondrial glutathione depletion in alcoholic liver disease.
Author
Fern]andez-Checa JC; Hirano T; Tsukamoto H; Kaplowitz N
Address
Division of Gastrointestinal and Liver Diseases' University of
Southern
California School of Medicine' Los Angeles.
Source
alcohol, 10(6):469-75 1993 Nov-Dec
Abstract
Alcoholic liver disease (ALD) is one the most serious consequences
of
chronic alcohol abuse. Liver cirrhosis' the culmination of the
illness'
is one of the leading causes of death in Western countries.
Mitochondria are a target of ethanol intoxication mainly due
to the
toxic effects of acetaldehyde' a byproduct of ethanol metabolism.
Morphological and functional changes in mitochondria are one
of the key
hallmarks of chronic ethanol exposure in both chronic alcoholics
and
experimental models of alcoholism. The functional changes observed
in
mitochondria from ethanol-treated animals are translated in an
overall
decrease in ATP levels resulting from a lower rate of ATP synthesis
as
a consequence of impaired processing at the translational level
of some
components of oxidative phosphorylation encoded by mitochondrial
DNA
genome. Mitochondrial glutathione (GSH) plays a critical role
in the
maintenance of cell functions and viability and in mitochondrial
physiology by metabolism of oxygen free radicals generated in
the
respiratory chain. GSH in mitochondria originates from cytosol
by a
transport system which translocates GSH into the matrix. This
transport
system is impaired in chronic ethanol-fed rats' which translates
in a
selective and significant depletion of the mitochondrial GSH
content
resulting in the development of an increased susceptibility to
oxidant
stress. Using the intragastric infusion model of experimental
ALD in
rats' the profound and selective mitochondrial GSH depletion
precedes
the onset of alcoholic liver disease' mitochondrial lipid peroxidation'
and progression of liver damage.(ABSTRACT TRUNCATED AT 250 WORDS)
Title
Gastric inJury and protection against alcohol and acid: influence
of
perturbations in glutathione metabolism.
Author
Smith GS; Tornwall MS; Barreto JC; Miller TA
Address
Department of Surgery' The University of Texas Medical School'
Houston
77030' USA.
Source
J Surg Res, 61(2):395-403 1996 Mar
Abstract
This study assessed the role that inhibition of glutathione (GSH)
synthesis and decreased GSH peroxidase (GPX) activity in the
rat played
in modulating gastric inJury induced by ethanol and acid and
its
prevention by 16'16-dimethyl PGE2 (dmPGE2) and the mild irritant'
25%
ethanol. Although numerous studies have proposed that GSH may
be
important in maintaining gastric mucosal defense' the exact role
of
this antioxidant in protecting the stomach from inJury remains
undefined. The present study addressed this consideration by
blocking
the synthesis of GSH and altering the maJor pathway by which
it
exhibits its antioxidant activity and determining the effect
of these
perturbations on gastric inJury and protection. Four to six rats
were
used for each experimental group. GSH synthesis was blocked by
the
potent and specific inhibitor L-buthionine sulfoximine (BSO)'
2 or 6
mmole/kg intraperitoneally. The activity of the maJor form of
GPX'
which is selenium dependent and utilizes GSH as a substrate to
detoxify
hydrogen peroxide and other hydroperoxides' was inhibited by
placing
animals on a selenium-deficient diet for 6 weeks. Gastric damage
was
induced by 100% ethanol' 50% ethanol in 150 mM HCl' and 0.75
M HCl.
Prevention of such inJury was accomplished with oral pretreatment
using
25% ethanol or dmPGE2 (5 microgram/kg). The damaging effects
of 100%
ethanol' 50% ethanol/150 mM HCl' or 0.75% M HCl were not adversely
affected by BSO pretreatment even though GSH synthesis was inhibited
by
as much as 80%. Similarly' inhibition of GPX activity by 58%
in adult
rats and 98% in weanling rats failed to potentiate the damaging
effect
of 100% ethanol. Furthermore' with both perturbations in GSH
metabolism' the protective action of dmPGE2 and 25% ethanol was
maintained. Our results indicate that profound alterations in
gastric
GSH metabolism by themselves do not aggrevate the inJurious effects
of
ethanol or acid' nor do they prevent the protective action of
a
prostaglandin or mild irritant.
Title
GSH transport in mitochondria: defense against TNF-induced oxidative
stress and alcohol-induced defect.
Author
Fern]andez-Checa JC; Kaplowitz N; Garc]ia-Ruiz C; Colell A; Miranda
M;
Mar]i M; Ardite E; Morales A
Address
Instituto de Investigaciones Biom]edicas' Hospital Clinic i Provincial'
Universidad de Barcelona' Spain.
Source
Am J Physiol, 273(1 Pt 1):G7-17 1997 Jul
Abstract
Mitochondria generate reactive oxygen species (ROS) as byproducts
of
molecular oxygen consumption in the electron transport chain.
Most
cellular oxygen is consumed in the cytochrome-c oxidase complex
of the
respiratory chain' which does not generate reactive species.
The
ubiquinone pool of complex III of respiration is the maJor site
within
the respiratory chain that generates superoxide anion as a result
of a
single electron transfer to molecular oxygen. Superoxide anion
and
hydrogen peroxide' derived from the former by superoxide dismutase'
are
precursor of hydroxyl radical through the participation of transition
metals. glutathione (GSH) in mitochondria is the only defense
available
to metabolize hydrogen peroxide. A small fraction of the total
cellular
GSH pool is sequestered in mitochondria by the action of a carrier
that
transports GSH from the cytosol to the mitochondrial matrix.
Mitochondria are not only one of the main cellular sources of
ROS' they
also are a key target of ROS. Mitochondria are subcellular targets
of
cytokines' especially tumor necrosis factor (TNF); depletion
of GSH in
this organelle renders the cell more susceptible to oxidative
stress
originating in mitochondria. Ceramide generated during TNF signaling
leads to increased production of ROS in mitochondria. Chronic
ethanol-fed hepatocytes are selectively depleted of GSH in mitochondria
due to a defective operation of the carrier responsible for transport
of GSH from the cytosol into the mitochondrial matrix. Under
these
conditions' limitation of the mitochondrial GSH pool represents
a
critical contributory factor that sensitizes alcoholic hepatocytes
to
the prooxidant effects of cytokines and prooxidants generated
by
oxidative metabolism of ethanol. S-adenosyl-L-methionine prevents
development of the ethanol-induced defect. The mitochondrial
GSH
carrier has been functionally expressed in Xenopus laevis oocytes
microinJected with mRNA from rat liver. This critical carrier
displays
functional characteristics distinct from other plasma membrane
GSH
carriers' such as its ATP dependency' inhibitor specificity'
and the
size class of mRNA that encode the corresponding carrier' suggesting
that the mitochondrial carrier of GSH is a gene product distinct
from
the plasma membrane transporters.
Title
Hepatic glutathione after ethanol administration in rat: effects
of
cimetidine and omeprazole.
Author
Battiston L; Tulissi P; Moretti M; Mazzoran L; Marchi P; Pussini
E;
Pozzato G
Address
Institute of Medicina Clinica' University of Trieste' School
of
Medicine' Italy.
Source
Pharmacol Res, 31(5):305-11 1995 May
Abstract
As a fraction of ingested ethanol (EtOH) is metabolized by gastric
mucosa' different amounts of alcohol reach the liver' when the
same
dose is administered by oral or intravenous route. In previous
experiments' we demonstrated that the decrease of hepatic reduced
glutathione (GSH) is less pronounced and is followed by a quicker
recovery after oral than after intraperitoneal administration
of the
same amount of EtOH. Therefore' the time-course of hepatic GSH
concentration seems to be an indirect assay of EtOH metabolism
by the
liver. On the basis of these findings' any condition causing
a reduced
function of gastric alcohol dehydrogenase (ADH) should show up
as a
more severe depletion of hepatic GSH. In the same rat experimental
model we determined the effects of cimetidine and omeprazole
administration on gastric ADH activity and on the time-course
of
hepatic GSH after EtOH load. Cimetidine was shown to inhibit
gastric
ADH with a Ki of 0.167 +/- 0.009 mmol l-1; accordingly' the
pretreatment with this drug (20 mg kg-1 b.w. per day for 1 week)
determined' after oral EtOH load' a marked reduction of hepatic
GSH'
likewise after intraperitoneal administration. Omeprazole exerted
only
a marginal inhibition on gastric ADH and this drug (0.3 mg kg-1
b.w.
per day for 1 week) did not modify the time-course of hepatic
GSH
concentrations after EtOH load. This study indicates that the
inhibition of gastric ADH' when associated with EtOH intake'
induces
depletion of the hepatic GSH concentration and' therefore' possible
liver damage.
Title
Protection against ethanol inJury in the canine stomach: role
of
mucosal glutathione.
Author
Victor BE; Schmidt KL; Smith GS; Miller TA
Address
Department of Surgery' University of Texas Medical School' Houston
77030
Source
Am J Physiol, 261(6 Pt 1):G966-73 1991 Dec
Abstract
The present study determined the role that mucosal glutathione
(GSH)
levels play in mediating the protective effects of a prostaglandin
and
a mild irritant against alcohol-induced gastric inJury. An in
vivo
canine chambered stomach preparation was used in which the exteriorized
mucosa was partitioned into two equal halves' one serving as
control.
Animals (5-8/group) received a subcutaneous inJection of either
normal
saline (NS) or the GSH depletor N-ethylmaleimide (NEM; 50 mg/kg)
and
then were assigned to one of a variety of groups based on the
perfusate
used to bathe the experimental side of the chamber; NS bathed
the
control mucosa. At completion of the studies' mucosa from each
side of
the chamber was assayed for total GSH (mumol/g wet wt) and evaluated
for microscopic damage. Both 16'16-dimethyl prostaglandin E2
(PGE2) (1
microgram/ml) and the mild irritant 8% ethanol' when topically
applied
to the gastric epithelium' increased mucosal GSH levels by
approximately 20% compared with control values' and elicited
no
deleterious effects to the mucosa. Treatment of animals with
NEM
prevented these GSH effects by PGE2 and 8% ethanol without damaging
the
mucosa. Application of 40% ethanol to the mucosa markedly reduced
levels of GSH and caused significant inJury to the mucosal surface'
much of it extending to the level of the gastric glands. When
mucosa
was pretreated with PGE2 or 8% ethanol before 40% ethanol exposure'
deep gastric gland inJury was virtually abolished. In animals
receiving
NEM' the protective effects of these agents against inJury by
40%
ethanol were prevented. Perturbations in tissue levels of GSH
under
these various experimental conditions failed to correlate
histologically with the status of gastric mucosal integrity.
Title
Antioxidant protection systems of rat lung after chronic ethanol
inhalation.
Author
Rikans LE; Gonzalez LP
Address
Department of Pharmacology' College of Medicine' University of
Oklahoma' Oklahoma City.
Source
alcohol Clin Exp Res, 14(6):872-7 1990 Dec
Abstract
The effect of chronic ethanol administration on pulmonary antioxidant
protection systems was investigated in male Sprague-Dawley rats
exposed
to room air or room air containing ethanol vapors for 5 weeks.
Blood
ethanol concentrations in ethanol-exposed rats were usually between
200
and 300 mg/dl. Glutathione' vitamin E' and malondialdehyde
concentrations were measured in lung homogenates' and antioxidant
enzyme activities (catalase' glutathione peroxidase' Cu/Zn-superoxide
dismutase' glutathione reductase) were determined in the supernatant
fractions. For comparison' the measurements were also made using
liver
fractions. ethanol treatment increased the activities of catalase
(117%) and Cu/Zn-superoxide dismutase (25%) in lung but not in
liver.
Although chronic ethanol inhalation lowered hepatic glutathione
(19%)
and hepatic vitamin E (33%)' there was no increase in malondialdehyde
content in either liver or lung of ethanol-exposed rats. The
elevation
of pulmonary antioxidant enzyme activities could be interpreted
to mean
that lung is a target for ethanol-induced oxidative stress. However'
as
there was no loss of pulmonary GSH or vitamin E and no increase
in
malondialdehyde formation' it appears that long-term ethanol
exposure
did not produce a significant degree of oxidative stress in rat
lung.
Title
Effect of ethanol-generated free radicals on gastric intrinsic
factor
and glutathione.
Author
Shaw S; Herbert V; Colman N; Jayatilleke E
Address
Department of Medicine' Mount Sinai School of Medicine' New York'
NY.
Source
alcohol, 7(2):153-7 1990 Mar-Apr
Abstract
The oxidation of acetaldehyde (generated from the metabolism
of
ethanol) by oxidases such as xanthine oxidase generates free
radicals
which can mobilize ferritin iron' alter hepatic glutathione and
produce
lipid peroxidation. The stomach' a site of ethanol metabolism
and rich
in xanthine oxidase' was studied with respect to the effects
of ethanol
on intrinsic factor (IF) binding of vitamin B-12 as well as gastric
glutathione (GSH). Incubations of gastric homogenates with
acetaldehyde-xanthine oxidase inhibited the B-12 binding ability
by IF.
A large acute dose of ethanol in vivo (5 g/kg' conc. greater
than 40%
w/v) decreased gastric IF binding of B-12 and depressed gastric
GSH;
these effects were markedly attenuated by the feeding of sodium
tungstate which inhibited xanthine oxidase. Changes in B-12 binding
paralleled changes in gastric GSH. Scatchard plots of IF binding
of
B-12 for homogenates suggested decreased number of binding sites
rather
than altered affinity. In conclusion' the gastric metabolism
of ethanol
generates free radicals which alter IF binding of B-12' depress
gastric
GSH and may play a role in alcohol-induced gastric inJury.
Title
Antioxidant defense system in lung of male and female rats:
interactions with alcohol' copper' and type of dietary carbohydrate.
Author
Fields M; Lewis CG; Lure MD
Address
Beltsville Human Nutrition Research Center' US Department of
Agriculture' Agricultural Research Service' MD 20705' USA.
Source
Metabolism, 45(1):49-56 1996 Jan
Abstract
Male and female rats were used to investigate the effects of
type of
dietary carbohydrate (CHO)' copper' and ethanol consumption on
lung
antioxidant enzyme activities and levels of phosphorylated compounds
in
whole blood. Copper-deficient female rats exhibited a greater
degree of
copper deficiency than males' as assessed by hepatic copper
concentration and hepatic copper superoxide dismutase (CuSOD)
activity.
However' copper-deficient male rats fed fructose-containing diets
exhibited greater growth retardation' anemia' and heart hypertrophy
than females consuming the same diets and males fed starch. In
addition' one of 10 copper-deficient male rats that ate a
fructose-based diet and drank water and one of 10 copper-deficient
male
rats that ate a starch-based diet and drank ethanol died.
Copper-deficient' starch-fed males exhibited the highest activities
of
glutathione peroxidase (GSH-Px) and catalase as compared with
fructose-fed rats. ethanol consumption elevated the activities
of
GSH-Px and catalase. Copper-deficient female rats exhibited higher
catalase but lower GSH-Px activities than males. It is suggested
that
in copper deficiency' the ability to increase antioxidant enzyme
activities in rats consuming starch is greater than in rats consuming
fructose. Rats fed starch are provided with a greater degree
of
protection against oxidative damage than rats fed fructose. In
addition' polyphosphorylated compounds in blood were reduced
in
copper-deficient male rats that consumed fructose-based diets.
This may
impair supply of oxygen to tissues. |
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