Studies on the fate of the glutathione and cysteine conjugates of acetaminophen in mice.
Studies were conducted in mice to examine the origin and fate of the amino acid-containing conjugates of acetaminophen (APAP). Collection of bile containing [14C]APAP metabolites (mainly the glutathione conjugate) in common duct-cannulated mice given a 250 mg/kg oral dose of the drug reduced by greater than 70% the urinary excretion of the cysteine and mercapturic acid conjugates of APAP. This confirmed previous reports which indicated that these urinary metabolites originated from the glutathione conjugate excreted in bile. The urinary excretion of cysteine and mercapturic acid conjugates was not altered, however, by ligation of the common bile duct in mice given APAP. Thus, biliary excretion of the glutathione conjugate is not obligatory for the appearance of cysteine and mercapturic acid conjugates in urine. Intravenous administration of purified glutathione conjugate to mice having a bile-duct cannula indicated that this conjugate did not appear in bile but appeared in urine primarily in the form of the cysteine conjugate. An identical pattern of excretion was observed after an iv dose of the purified cysteine conjugate of APAP to bile duct-cannulated mice. These results indicated that, if the glutathione conjugate leaves the liver via the blood, it is rapidly converted to the cysteine conjugate which is eliminated in urine. This conversion takes place at multiple sites in the body and evidence is presented to implicate both intestine and kidney in the process. The appearance of a small amount of glutathione conjugate in urine (16%) after an iv dose of the cysteine conjugate indicates that formation of the glutathione of APAP can occur by a route that does not involve direct conjugation of reactive metabolites of the drug with glutathione.
Fischer
L J
LJ
Green
M D
MD
Harman
A W
AW
D000082:Acetaminophen / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000378:metabolism* / Q000652:urine; D000818:Animals; D003545:Cysteine / Q000378:metabolism* / Q000652:urine; D005978:Glutathione / Q000378:metabolism* / Q000652:urine; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice
D000082:Acetaminophen; C037386:acetaminophen glucuronide; D005978:Glutathione; D003545:Cysteine; C034780:3-(glutathion-S-yl)acetaminophen