Characterization of binding of N'-nitrosonornicotine to protein
The NADPH-dependent activation of the carcinogenic nitrosamine, N'-nitrosonornicotine (NNN) to a reactive intermediate which binds covalently to protein was assessed using male Sprague-Dawley rat liver and lung microsomes. The NADPH-dependent covalent binding of (/sup 14/C)NNN to liver and lung microsomes was linear with time up to 90 and 45 min, respectively and was also linear with protein concentrations up to 3.0 and 2.0 mg/ml, respectively. The apparent K/sub m/ and V/sub max/ of the NADPH-dependent binding to liver microsomes were determined from the initial velocities. Addition of the thiols glutathione, cystein, N-acetylcysteine or 2-mercapthoethanol significantly decreased the non-NADPH-dependent binding to liver microsomal protein, but did not affect the NADPH-dependent binding. Glutathione was required in order to observe any NADPH-dependent binding to lung microsomal protein. In lung microsomes, SKF-525A significantly decreased the NADPH-dependent binding by 79%. Replacement of an air atmosphere with N/sub 2/ or CO:O/sub 2/ (8:2) significantly decreased the NADPH-dependent binding of (/sup 14/C)NNN to liver microsomal protein by 40% or 27% respectively. Extensive covalent binding of (/sup 14/C)NNN to liver and muscle microsomal protein occurred in the absence of an NADPH-generating system, in the presence of 50% methanol and also to bovine serum albumin, indicating a nonenzymatic reaction. These data indicate that cytochrome P-450 is at least in part responsible for the metabolic activation of the carcinogen NNN, but also suggest additional mechanisms of activation.
- Research Organization:
- Kentucky Univ., Lexington (USA)
- OSTI ID:
- 6713093
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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CARBON 14 COMPOUNDS
CONFIGURATION INTERACTION
MICROSOMES
BIOCHEMICAL REACTION KINETICS
NADP
BIOCHEMISTRY
NITROSAMINES
METABOLIC ACTIVATION
LIVER
LUNGS
MUSCLES
PROTEINS
RATS
AMINES
ANIMALS
BODY
CELL CONSTITUENTS
CHEMISTRY
COENZYMES
DIGESTIVE SYSTEM
GLANDS
KINETICS
LABELLED COMPOUNDS
MAMMALS
NITROSO COMPOUNDS
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOIDS
ORGANS
REACTION KINETICS
RESPIRATORY SYSTEM
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques