Probing the Mechanism of the Carcinogenic Activation of N-Nitrosodiethanolamine with Deuterium Isotope Effects: In Vivo Induction of DNA Single-Strand Breaks and Related in Vitro Assays
详细信息 查看全文
- 作者：Richard N. Loeppky ; Anne Fuchs ; Christine Janzowski ; Christina Humberd ; Petra Goelzer ; Heiko Schneider ; and Gerhard Eisenbrand
- 刊名：Chemical Research in Toxicology
- 出版年：1998
- 出版时间：December 1998
- 年：1998
- 卷：11
- 期：12
- 页码：1556 - 1566
- 全文大小：148K
- 年卷期：v.11,no.12(December 1998)
- ISSN：1520-5010
文摘
A series of bioassays, including in vivo induction of DNA single-strand breaks (SSB) andcytotoxicity in cytochrome P450 2E1-transfected cells, were utilized with N-nitrosodiethanolamine (NDELA), its deuterated isotopomers (
-D4NDELA and 
-D4NDELA), N-nitroso-2-hydroxymorpholine (NHMOR), and two of its deuterated isotopomers (2-D-NHMOR and 5,5-D2-NHMOR) to probe the mechanism of carcinogenic activation of NDELA and the role of itsmetabolite NHMOR. DNA samples, taken from the livers of male Wistar rats 4 h after theadministration of NDELA, exhibited dose-dependent DNA SSB levels over the range of 0.08-0.75 mmol/kg (body weight), with the greatest SSB level at the highest dose. Deuterium isotopeeffects on DNA SSB levels were inversely dependent on dose: -D4NDELA, 3.22-1.37; and-D4NDELA, 1.38-0.79. At the lowest dose of 0.15 mmol/kg (body weight), 5,5-D2-NHMORgave an isotope effect for DNA SSB of 2.8 while that for 2-D-NHMOR was 0.7. NDELA and-D4NDELA were equally cytotoxic to human P450 2E1-transfected V79 Chinese hamster cells,while -D4NDELA was not. Significant DNA SSB levels were observed in these cells forNDELA and -D4NDELA but not for -D4NDELA. A kinetic deuterium isotope effect of 2.6for Vmax/Km was observed for the horse liver alcohol dehydrogenase-mediated oxidation of -D4NDELA to NHMOR, while kH/kD for -D4NDELA was 1.05. These data provide the firstdefinitive evidence for the activation of NDELA by a pathway involving the scission of the-CH bond and are consistent with P450 2E1-mediated -hydroxylation of NDELA producingthe corresponding reactive -hydroxynitrosamine.
-D4NDELA and -D4NDELA), N-nitroso-2-hydroxymorpholine (NHMOR), and two of its deuterated isotopomers (2-D-NHMOR and 5,5-D2-NHMOR) to probe the mechanism of carcinogenic activation of NDELA and the role of itsmetabolite NHMOR. DNA samples, taken from the livers of male Wistar rats 4 h after theadministration of NDELA, exhibited dose-dependent DNA SSB levels over the range of 0.08-0.75 mmol/kg (body weight), with the greatest SSB level at the highest dose. Deuterium isotopeeffects on DNA SSB levels were inversely dependent on dose: -D4NDELA, 3.22-1.37; and-D4NDELA, 1.38-0.79. At the lowest dose of 0.15 mmol/kg (body weight), 5,5-D2-NHMORgave an isotope effect for DNA SSB of 2.8 while that for 2-D-NHMOR was 0.7. NDELA and-D4NDELA were equally cytotoxic to human P450 2E1-transfected V79 Chinese hamster cells,while -D4NDELA was not. Significant DNA SSB levels were observed in these cells forNDELA and -D4NDELA but not for -D4NDELA. A kinetic deuterium isotope effect of 2.6for Vmax/Km was observed for the horse liver alcohol dehydrogenase-mediated oxidation of -D4NDELA to NHMOR, while kH/kD for -D4NDELA was 1.05. These data provide the firstdefinitive evidence for the activation of NDELA by a pathway involving the scission of the-CH bond and are consistent with P450 2E1-mediated -hydroxylation of NDELA producingthe corresponding reactive -hydroxynitrosamine.