Synthesis rates of glutathione and activated sulphate (PAPS) and response to cysteine and acetaminophen administration in glutathione-depleted rat hepatocytes.
The effects of cysteine and acetaminophen (AA) on the synthesis rates of glutathione (GSH), adenosine 3'-phosphate 5'-phosphosulphate (PAPS, activated sulphate) and the AA metabolites, AA-GSH and AA-sulphate were studied in rat hepatocytes depleted of GSH by diethyl maleate (DEM). The synthesis rates were determined simultaneously by a previously described radioactive tracer method. Preincubation of the hepatocytes with 0.7 mM DEM for 30 min depleted GSH by 59% (P < 0.05) and PAPS by 28% (P < 0.05). Incubation with a toxic AA concentration resulted in GSH synthesis at a rate of 95 nmol/(10(6) cells.min) which increased to 281 nmol/(10(6) cells.min) (P = 0.05) after addition of cysteine. However, increased GSH synthesis was not followed by increased AA-GSH synthesis [4.7 vs 4.8 nmol/(10(6) cells.hr)]. Also, PAPS synthesis increased after cysteine administration [10.2 to 19.1 nmol/(10(6) cells.min)] (P < 0.05) without any change in AA-sulphate synthesis 18.5 vs 18.3 nmol/(10(6) cells.hr)]. Thus, in contrast to hepatocytes with normal GSH concentration, cysteine stimulated both GSH and PAPS synthesis rates in GSH-depleted rat hepatocytes incubated with a toxic AA concentration without stimulation of AA-GSH or AA-sulphate synthesis rates, indicating that the hepatoprotective effect of cysteine on AA toxicity is primarily due to stimulation of a GSH-mediated reduction of the reactive AA metabolite N-acetyl-p-benzoquinoneimine back to AA.
Dalhoff
K
K
Department of Medicine A-2152 Rigshospitalet, Copenhagen, Denmark.
Poulsen
H E
HE
D000082:Acetaminophen / Q000633:toxicity*; D000818:Animals; D002478:Cells, Cultured; D003545:Cysteine / Q000494:pharmacology*; D005978:Glutathione / Q000096:biosynthesis* / Q000172:deficiency; D008099:Liver / Q000187:drug effects*; D008298:Maleates; D010724:Phosphoadenosine Phosphosulfate / Q000096:biosynthesis*; D051381:Rats
D008298:Maleates; D000082:Acetaminophen; D010724:Phosphoadenosine Phosphosulfate; C014476:diethyl maleate; D005978:Glutathione; D003545:Cysteine