title: Evidence that a hemoglobin adduct used for dosimetry of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone is a carboxylic ester.
abstract: Hemoglobin adducts of the carcinogenic tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) release 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB) upon mild base or acid hydrolysis. HPB has been detected in hydrolysates of hemoglobin from smokers and snuff dippers and has been proposed as a dosimeter of exposure to and metabolic activation of NNK in people exposed to tobacco products. In this study, labeling experiments were carried out with [18O]NaOH that provide strong evidence that the globin adduct that releases HPB upon hydrolysis is a carboxylic ester. Globin was isolated from rats treated with [5-3H]NNK. This globin was reacted with NaCNBH3, followed by hydrolysis at room temperature with 0.2 N NaOH. Analysis of the products demonstrated the presence of 4-hydroxy-1-(3-pyridyl)-1-butanol, but not HPB. These results demonstrate that the adduct in globin has a free carbonyl group and is not a Schiff base. This sequence of reactions was then carried out with [18O]NaOH under conditions that were shown to result in incorporation of 18O if nucleophilic displacement at C-4 had occurred. Analysis by GC-MS of the 4-hydroxy-1-(3-pyridyl)-1-butanol formed in this experiment demonstrated that there was no incorporation of 18O. These results are consistent only with the hydrolysis of an ester by a BAC2 mechanism. Therefore, the adduct releasing HPB upon mild base hydrolysis must be a 4-(3-pyridyl)-4-oxobutyl ester of aspartate, glutamate, or a terminal carboxylate.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Chemical Carcinogenesis, American Health Foundation, Valhalla, NY 10595.
authors.forename: S G
authors.initials: SG
authors.lastname: Carmella
authors.forename: S S
authors.initials: SS
authors.lastname: Kagan
authors.forename: S S
authors.initials: SS
authors.lastname: Hecht
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000008:administration & dosage / Q000032:analysis / Q000633:toxicity; D005914:Globins / Q000032:analysis / Q000737:chemistry / Q000187:drug effects; D006454:Hemoglobins / Q000032:analysis / Q000737:chemistry / Q000187:drug effects*; D009602:Nitrosamines / Q000008:administration & dosage / Q000032:analysis / Q000633:toxicity*; D051381:Rats
chemical_list: D002273:Carcinogens; D006454:Hemoglobins; D009602:Nitrosamines; C016583:4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone; D005914:Globins