Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.10.2 (focal adhesion kinase)
 44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

N-Nitrosopyrrolidine (NPYR) is a hepatocarcinogen in rats. It is metabolically activated by cytochrome P450 enzymes in the liver leading to the formation of 4-oxobutanediazohydroxide (4) and related intermediates that react with DNA to form adducts. Because DNA adducts are thought to be critical in carcinogenesis by NPYR, we analyzed hepatic DNA of NPYR-treated rats for several adducts: N2-(tetrahydrofuran-1-yl)dGuo (N2-THF-dGuo, 13), N6-THF-dAdo (14), N4-THF-dCyd (17), and dThd adducts 15 and 16. The rats were treated with NPYR in the drinking water, 600 ppm for 1 week, or 200 ppm for 4 or 13 weeks. Hepatic DNA was isolated, enzymatically hydrolyzed, and analyzed by capillary LC-ESI-MS-SIM, which indicated the presence of adducts 13, 14, and 17. Because these adducts can be unstable at the deoxyribonucleoside level, further analyses were carried out using DNA treated with NaBH3CN, which converts adducts 13-17 to N2-(4-hydroxybut-1-yl)dGuo [N2-(4-HOB)dGuo, 18], N6-(4-HOB)dAdo (19), O2-(4-HOB)dThd (20), O4-(4-HOB)dThd (21), and N4-(4-HOB)dCyd (22). [15N]-Labeled analogues of adducts 18-20 and 22 were synthesized and used in this analysis, which was performed by capillary LC-ESI-MS/MS-SRM. Convincing evidence for the presence of adducts 18-22 was obtained. Levels of 18, 19, 20, and 21 were (mumol/mol dGuo): 3.41-5.39, 0.02-0.04, 2.56-3.87, and 2.28-5.05, respectively. Compound 22 was not quantified due to interfering peaks. These results provide the first evidence for tetrahydrofuranyl-substituted DNA adducts in the livers of rats treated with NPYR. The finding of dAdo and dThd adducts is of particular interest since previous studies have shown that NPYR causes mutations at AT base pairs in DNA of rat liver.
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PMID:Analysis of adducts in hepatic DNA of rats treated with N-nitrosopyrrolidine. 1739 61

The well established rat hepatocarcinogen N-nitrosopyrrolidine (NPYR, 1) requires metabolic activation to DNA adducts to express its carcinogenic activity. Among the NPYR-DNA adducts that have been identified, the cyclic 7,8-butanoguanine adduct 2-amino-6,7,8,9-tetrahydro-9-hydroxypyrido[2,1-f]purine-4(3H)-one (6) has been quantified using moderately sensitive methods, but its levels have never been compared to those of other DNA adducts of NPYR in rat hepatic DNA. Therefore, in this study, we developed a sensitive new LC-ESI-MS/MS-SRM method for the quantitation of adduct 6 and compared its levels to those of several other NPYR-DNA adducts formed by different mechanisms. The new method was shown to be accurate and precise, with good recoveries and low fmol detection limits. Rats were treated with NPYR by gavage at doses of 46, 92, or 184 mg/kg body weight and sacrificed 16 h later. Hepatic DNA was isolated and analyzed for NPYR-DNA adducts. Adduct 6 was by far the most prevalent, with levels ranging from about 900-3000 micromol/mol Gua and responsive to dose. Levels of adducts formed from crotonaldehyde, a metabolite of NPYR, were about 0.2-0.9 micromol/mol dGuo, while those of adducts resulting from reaction with DNA of tetrahydrofuranyl-like intermediates were in the range of 0.01-4 micromol/mol deoxyribonucleoside. The results of this study demonstrate that, among typical NPYR-DNA adducts, adduct 6 is easily the most abundant in hepatic DNA. Since previous studies have shown that it can be detected in the urine of NPYR-treated rats, the results suggest that it is a potential candidate as a biomarker for assessing human exposure to and metabolic activation of NPYR.
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PMID:Mass spectrometric analysis of a cyclic 7,8-butanoguanine adduct of N-nitrosopyrrolidine: comparison to other N-nitrosopyrrolidine adducts in rat hepatic DNA. 1976 Dec 53