Effect of anisotonic cell-volume modulation on glutathione-S-conjugate release, t-butylhydroperoxide metabolism and the pentose-phosphate shunt in perfused rat liver.
1. Addition of 1-chloro-2,4-dinitrobenzene to isolated perfused rat liver results in the rapid formation of its glutathione-S-conjugate [S-(2,4-dinitrophenyl)glutathione], which is released into both, bile and effluent perfusate. Anisotonic perfusion did not affect total S-conjugate formation, but release of the S-conjugate into the perfusate was increased (decreased) following hypertonic (hypotonic) exposure at the expense of excretion into bile. Stimulation of S-conjugate release into the perfusate following hypertonic exposure paralleled the time course of volume-regulatory net K+ uptake. 2. Basal steady-state release of oxidized glutathione (GSSG) into bile was 1.30 +/- 0.12 nmol.g-1.min-1 (n = 18) during normotonic (305 mOsmol/l) perfusion and was 3.8 +/- 0.3 nmol.g-1.min-1 in the presence of t-butylhydroperoxide (50 mumol/l). Hypotonic exposure (225 mOsmol/1) lowered both, basal and t-butylhydroperoxide (50 mumol/l)-stimulated GSSG release into bile by 35% and 20%, respectively, whereas hypertonic exposure (385 mOsmol/l) increased. Anisotonic exposure was without effect on t-butylhydroperoxide removal by the liver. GSSG release into bile also decreased by 33% upon liver-cell swelling due to addition of glutamine plus glycine (2 mmol/l, each). 3. Hypotonic exposure led to a persistent stimulation 14CO2 production from [1-14C]glucose by about 80%, whereas 14CO2 production from [6-14C]glucose increased by only 10%. Conversely, hypertonic exposure inhibited 14CO2 production from [1-14C]glucose by about 40%, whereas 14CO2 production from [6-14C]glucose was unaffected. The effect of anisotonicity on 14CO2 production from [1-14C]glucose was also observed in presence of t-butylhydroperoxide (50 mumol/l), which increased 14CO2 production from [1-14C]glucose by about 40%. 4. t-Butylhydroperoxide (50 mumol/l) was without significant effect on volume-regulatory K+ fluxes following exposure to hypotonic (225 mOsmol/l) or hypertonic (385 mOsmol/l) perfusate. Lactate dehydrogenase release from perfused rat liver under the influence of t-butylhydroperoxide was increased by hypertonic exposure compared to hypotonic perfusions. 5. The data suggest that hypotonic cell swelling stimulates flux through the pentose-phosphate pathway and diminishes loss of GSSG under conditions of mild oxidative stress. Hypotonically swollen cells are less prone to hydroperoxide-induced lactate dehydrogenase release than hypertonically shrunken cells. Hypertonic cell shrinkage stimulates the excretion of glutathione-S-conjugates into the sinusoidal circulation at the expense of biliary secretion.
Saha
N
N
Medizinische Universitätsklinik Freiburg, Federal Republic of Germany.
Stoll
B
B
Lang
F
F
Häussinger
D
D
D000818:Animals; D001646:Bile / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D004137:Dinitrochlorobenzene / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005973:Glutamine / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism*; D005998:Glycine / Q000494:pharmacology; D007038:Hypotonic Solutions; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D010427:Pentose Phosphate Pathway; D010477:Perfusion; D010545:Peroxides / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D020122:tert-Butylhydroperoxide
D004137:Dinitrochlorobenzene; D007038:Hypotonic Solutions; D010545:Peroxides; D005973:Glutamine; D002245:Carbon Dioxide; D020122:tert-Butylhydroperoxide; D005978:Glutathione; D005947:Glucose; D005998:Glycine