Biomedical subjects

T E Spratt

Publications and source records attributed to T E Spratt.

24 records · Page 2Linked to original sources

PubMed1989

Identification of sulfate and glucuronic acid conjugates of the 5-hydroxy derivative as major metabolites of 2-amino-3-methylimidazo[4,5-f]quinoline in rats.

New metabolites of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a potent mutagen and carcinogen formed during cooking of meat or fish, have been identified and quantitated in the urine and bile of rats. Administration was either by a pulse gavage dose of 40 mg/kg [2-14C]IQ or by dietary intake of 300 ppm IQ for 6 weeks. The metabolites were isolated by high-performance liquid chromatography and quantitated by radioactivity. They were then characterized by their resistance or sensitivity to hydrolytic enzymes or acid hydrolysis, by nuclear magnetic resonance and mass spectrometry, or coinjection with a synthetic sample. A minor metabolite was the IQ N-glucuronide. A major metabolite was formed by hydroxylation of IQ at the 5-position; it was present in urine and bile and was conjugated as the glucuronide or sulfate ester, which together accounted for about 40% of urinary or biliary metabolites. The unconjugated compound partially adsorbs onto the high-performance liquid chromatographic columns used. The amounts of 5-OH-IQ present as conjugates in urine or bile were similar, irrespective of mode of administration. Thus, hydroxylation of IQ on carbon 5 followed by type II conjugation reactions yields quantitatively important metabolic products.

Animals↗

PubMed1988

Evidence for 4-(3-pyridyl)-4-oxobutylation of DNA in F344 rats treated with the tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N'-nitrosonornicotine.

DNA was isolated from tissues of F344 rats 24 h after treatment by s.c. injection with [5-3H]4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone ([5-3H]NNK) or [5-3H]N'-nitrosonornicotine ([5-3H]NNN). It was hydrolyzed with acid or at pH 7, 100 degrees C, and the hydrolysates were analyzed by HPLC. The major product in each case was identified as 4-hydroxy-1-(3-pyridyl)-1-butanone, formed by hydrolysis of a DNA adduct. It was detected in DNA from the livers of rats treated with [5-3H]NNK or [5-3H]NNN, and in DNA from lungs of rats treated with [5-3H]NNK. These results demonstrate that 4-(3-pyridyl)-4-oxobutylation of DNA occurs in rats treated with NNK or NNN, and are consistent with the hypothesis that these nitrosamines are metabolically activated by alpha-hydroxylation.

Animals↗

PubMed1988

Approaches to the development of assays for interaction of tobacco-specific nitrosamines with haemoglobin and DNA.

The tobacco-specific, nicotine-derived nitrosamines 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) are among the most important carcinogens in tobacco and tobacco smoke. Treatment of Fischer 344 rats with these carcinogens resulted in alkylation of haemoglobin and DNA by the 4-(3-pyridyl)-4-oxobutyl group formed during their metabolism. This alkyl group can be detached from globin or DNA under mild hydrolytic conditions as 4-hydroxy-1-(3-pyridyl)-1-butanone, which appears to be a potentially useful dosimeter for human exposure to, and activation of, tobacco-specific nitrosamines.

Animals↗

PubMedDate not supplied

Analysis for N2-(pyridyloxobutyl)deoxyguanosine adducts in DNA of tissues exposed to tritium-labeled 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N'-nitrosonornicotine.

The tobacco-specific carcinogens 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) are metabolically activated to DNA binding intermediates, partially via 4-(3-pyridyl)-4-oxobutanediazohydroxide (7) or related carbonium ions. Previous studies have shown that generation of 7 from 4-(carbethoxynitrosamino)-1-(3-pyridyl)-1-butanone (11) in the presence of deoxyguanosine yields a major adduct identified as 2'-deoxy-N-[1-methyl-3-oxo-3-(3-pyridyl)propyl]guanosine (adduct 1). These results suggested that adduct 1 should be present in DNA of tissues that can metabolically activate NNK and NNN. In the present study, we evaluate the formation of adduct 1 and its structurally related straight-chain analogue 2'-deoxy-N-[4-oxo-4-(3-pyridyl)butyl]guanosine (adduct 2) in DNA of tissues of rats treated with [5-3H]NNK or [5-3H]NNN, and in DNA of nasal mucosa that had been cultured in medium containing [5-3H]NNK or [5-3H]NNN. Hepatic DNA from rats treated with [5-3H]NNK was enzymatically hydrolyzed to deoxyribonucleosides and analyzed by HPLC. One of the radioactive peaks, peak E, coeluted with adduct 1. However, treatment of peak E with NaBH4 resulted in the formation of products different from those produced by NaBH4 treatment of adduct 1, demonstrating that adduct 1 could not be detected under these conditions. Hydrolysis of peak E with acid produced 4-hydroxy-1-(3-pyridyl)-1-butanone (9), suggesting that peak E might be adduct 2. Therefore, adduct 2 was synthesized by reaction of deoxyguanosine with 1-(3-pyridyl)butane-1,4-dione (5) in the presence of NaCNBH3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Solvolysis of model compounds for alpha-hydroxylation of N'-nitrosonornicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone: evidence for a cyclic oxonium ion intermediate in the alkylation of nucleophiles.

N'-Nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), two potent tobacco-specific carcinogens, have been previously found to pyridyloxobutylate DNA. The adducts were found to be unstable and have not been fully characterized. In order to gain an understanding of the chemistry of the pyridyloxobutylating species, five model pyridyloxobutylating agents have been solvolyzed and the products identified. 4-[(Acetoxymethyl)-nitrosamino]-1-(3-pyridyl)-1-butanone (3), 4-(carbethoxynitrosamino)-1-(3-pyridyl)-1-butanone (4), 4-oxo-4-(3-pyridyl)-1-butyl p-toluenesulfonate (16), 2-chloro-2-(3-pyridyl)-2,3,4,5-tetrahydrofuran (17), and 4-[(acetoxymethyl)nitrosamino]-1-(3-pyridyl)-1-butanol (20) were solvolyzed in buffer and in buffer containing 20% MeOH. The solvolyses of 16 and 17 in H2O produced only 4-hydroxy-1-(3-pyridyl)-1-butanone (7). In the presence of 20% MeOH, 7 and 2-methoxy-2-(3-pyridyl)-2,3,4,5-tetrahydrofuran (12) were produced from 16 and 17 in a 4:1 ratio. The solvolysis of 3 and 4 in the presence of esterase gave similar products. 4-Methoxy-1-(3-pyridyl)-1-butanone (8) was not detected as a product. In the absence of MeOH, compound 7, 3-pyridyl cyclopropyl ketone (10), and 1-(3-pyridyl)-but-2-en-1-one (18) were observed. In the presence of MeOH, 12 was also formed and the ratio of 7 to 12 was again about 4:1. The esterase-catalyzed hydrolysis of 20 yielded 1-(3-pyridyl)-1,4-butanediol (22), 1-(3-pyridyl)-1,3-butanediol (27), 1-(3-pyridyl)-but-3-en-1-ol (25), 1-(3-pyridyl)but-2-en-1-ol (26), and 2-(3-pyridyl)-2,3,4,5-tetrahydrofuran (24).(ABSTRACT TRUNCATED AT 250 WORDS)

Alkylation↗

PubMedDate not supplied

Gastric carcinogenesis: 2-chloro-4-methylthiobutanoic acid, a novel mutagen in salted, pickled Sanma hiraki fish, or similarly treated methionine.

The customary salting and pickling of fish in high risk gastric cancer regions were modeled to explore the relevant causative chemicals. The fish Sanma hiraki was treated with sodium chloride and sodium nitrite at pH 3. Previously, it had been found that an extract of the treated fish was mutagenic in Salmonella typhimurium TA 1535 without S9 and also that it induced glandular stomach cancer upon gavage to rats. We now demonstrate that the mutagenicity was enhanced by preincubation of the raw meat for several days before salt-nitrite treatment. HPLC techniques showed that three mutagens were present in the fish extract. One of the mutagens was found to be stable over the pH range of 1.0-9.0. This mutagen was purified by silica gel solid phase extraction, followed by a series of reverse phase HPLC steps, and was characterized by low and high resolution MS, NMR, and FT-IR. While N-nitroso compounds were generally believed to be associated with gastric carcinogenesis, it was unexpectedly found that the mutagen has the novel structure 2-chloro-4-methylthiobutanoic acid (CMBA). Based on the structure, it seemed likely that methionine might be the precursor, and this was, indeed, proven. Both salt and nitrite are essential factors for forming this mutagen. The yield of CMBA was linear for chloride concentrations from 0 to 800 mM NaCl. Of 20 amino acids reacted with nitrite and chloride at pH 3, only methionine generated a mutagen for S. typhimurium TA 1535. Tryptophan gave a product mutagenic in S. typhimurium TA 100 and TA 98, but not TA 1535, and in the case of tyrosine, the mutagen was active only for TA 100. These results suggest an important role for salt in gastric carcinogenesis and provide new approaches for exploring the formation of mutagens/carcinogens for specific target organs.

Amino Acids↗