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Metabolism and disposition of benzidine in the dog
V M Lakshmi1, M B Mattammal, L A Spry
1Geriatric Research, Education and Clinical Center (GRECC), Veterans Administration Medical Center, St Louis, MO 63125.
Carcinogenesis
|January 1, 1990
Summary
Dogs metabolize benzidine differently than expected, with longer persistence in plasma and significant DNA binding in organs like the bladder. Further research is needed to identify the metabolic pathways involved in aromatic amine carcinogenicity.
Area of Science:
- Toxicology
- Pharmacokinetics
- Carcinogenesis
Background:
- Dogs serve as a relevant animal model for studying aromatic amine-induced bladder cancer.
- Understanding benzidine metabolism and disposition in dogs is crucial for cancer research.
Purpose of the Study:
- To assess the metabolism and disposition of benzidine in dogs.
- To investigate the pharmacokinetic profile and identify metabolites of benzidine.
Main Methods:
- Dogs were administered an intravenous dose of radiolabeled benzidine ([3H]benzidine).
- Plasma half-life, distribution of radioactivity in organs (bile, urine, carcass, bladder), and DNA binding were analyzed.
- High-performance liquid chromatography (HPLC) was used to identify benzidine and its metabolites in urine and bile.
Main Results:
- The plasma half-life of radiolabeled benzidine (including metabolites) was significantly longer (approx. 3 hours) than authentic benzidine (<30 min).
- The majority of radioactivity was found in bile, urine, and carcass within 5 hours.
- Significant radioactivity was detected in DNA from liver, kidney, and bladder, with the highest concentration in bladder transitional epithelium.
- Unmetabolized benzidine constituted about 30% of radioactivity in urine and bile; 3-hydroxybenzidine was a major metabolite in bile but not urine.
Conclusions:
- Benzidine undergoes considerable metabolism in dogs via undetermined pathways.
- The disposition and DNA binding patterns in dogs provide insights into aromatic amine-induced bladder cancer mechanisms.
- Further studies are required to elucidate the specific metabolic pathways of benzidine in this animal model.