HOMEPRODUCTSCOMPANYCONTACTFAQResearchDictionaryPharmaSign Up FREE or Login

Formation and disposition of nitrosochloramphenicol in rat liver.

Abstract
It has been suggested that in the chloramphenicol-induced aplastic anemia nitrosochloramphenicol may be involved as a toxic intermediate. We found that aminochloramphenicol, which reportedly is formed from chloramphenicol by intestinal bacteria, is N-oxygenated by liver microsomes of untreated rats with apparent Km = 0.4 mM and Vmax = 0.28 nmole/min/mg protein. These values are in close agreement with those reported for aniline N-oxygenation. Reductive reactions, however, eliminate the N-oxygenation products at markedly higher rates. As judged from hemoglobin-free single-pass liver perfusion experiments, N-hydroxy-chloramphenicol is reduced at rates faster than 300 nmole/min/g liver wet, and nitrosochloramphenicol is eliminated at rates faster than 1.5 mumole/min/g liver. At least two NADPH- and two NADH-dependent cytosolic enzymes are responsible for nitrosochloramphenicol reduction. Determination of the kinetic parameters of these enzymes by stop-flow analysis revealed the contribution of enzymes, one of it being alcohol dehydrogenase, with Michaelis constants in the micromolar range. Despite this high reducing capacity, about 10% of nitrosochloramphenicol reacted with GSH under formation of glutathionesulfinamidochloramphenicol and GSSG released from the liver into bile and venous effluent. At high nitrosochloramphenicol load these reactions led to glutathione depletion of the liver, caused membrane damage, and impaired bile production. At low nitrosochloramphenicol load, i.e. below 0.5 mumole/min/g, no relevant nitrosochloramphenicol passed the liver. These data together with the previously reported reactions of nitrosochloramphenicol within human blood suggest that nitrosochloramphenicol, if formed at all in the intestine or liver, is rather unlikely to be transferred to the critical target.
AuthorsM Ascherl, P Eyer, H Kampffmeyer
JournalBiochemical pharmacology (Biochem Pharmacol) Vol. 34 Issue 20 Pg. 3755-63 (Oct 15 1985) ISSN: 0006-2952 [Print] England
PMID4052115 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Carbon Radioisotopes
  • Chloramphenicol
  • nitrosochloramphenicol
  • Glutathione
  • Oxygen
Topics
  • Administration, Oral
  • Animals
  • Biotransformation
  • Carbon Radioisotopes
  • Chloramphenicol (analogs & derivatives, metabolism)
  • Chromatography, High Pressure Liquid
  • Glutathione (metabolism)
  • Kinetics
  • Male
  • Microsomes, Liver (drug effects, metabolism)
  • Oxygen (pharmacology)
  • Rats
  • Rats, Inbred Strains

Join CureHunter, for free Research Interface BASIC access!

Take advantage of free CureHunter research engine access to explore the best drug and treatment options for any disease. Find out why thousands of doctors, pharma researchers and patient activists around the world use CureHunter every day.
Realize the full power of the drug-disease research graph!


Choose Username:
Email:
Password:
Verify Password:
Enter Code Shown: