Detail of "20535-83-5"

Reference

Effect of protein diet on age-dependent methylation of liver nuclear components of mice administered N-nitrosodimethylamine

Effect of protein diet on age-dependent methylation of liver nuclear components of mice administered N-nitrosodimethylamine. Klaude, Maria; Von der Decken, Alexandra (Wenner-Gren Inst. Exp. Biol., Univ. Stockholm, Stockholm S-113 45, Swed.). JNCI, J. Natl. Cancer Inst., 73(4), 909-13 (English) 1984. CODEN: JJIND8. ISSN: 0198-0157. DOCUMENT TYPE: Journal CA Section: 18 (Animal Nutrition) Protein diets deficient or enriched in DL-methionine [59-51-8] were studied for the effect of methylation of nuclear components in subadult and adult outbred albino male mice given N-nitrosodimethylamine [62-75-9]. After the mice were fed diets for 6 days, they were given i.p. injections of [14C]N-nitrosodimethylamine (5 mg/kg body wt.) and killed 45 min later. Liver nuclei were isolated; incorporation of 14C into nuclear proteins and methylation of DNA and RNA were detd. In the subadult and adult animals the nuclear protein content was diminished by shortage of a single essential amino acid. Incorporation of 14C into the total protein was reduced. The redn. averaged 55% in the subadult and 23% in the adult animals. Neither an age-dependent nor a diet-dependent change in the specific methylation of DNA and RNA was obsd. Anal. of methylated purine bases showed an age-related rise in O6-methylguanine [20535-83-5] in the adult as compared with the subadult mice.

Comparison of the rates of repair of O6-alkylguanines in DNA by rat liver and bacterial O6-alkylguanine-DNA alkyltransferase

Comparison of the rates of repair of O6-alkylguanines in DNA by rat liver and bacterial O6-alkylguanine-DNA alkyltransferase. Pegg, Anthony E.; Scicchitano, David; Dolan, M. Eileen (Coll. Med., Pennsylvania State Univ., Hershey, PA 17033, USA). Cancer Res., 44(9), 3806-11 (English) 1984. CODEN: CNREA8. ISSN: 0008-5472. DOCUMENT TYPE: Journal CA Section: 4 (Toxicology) Section cross-reference(s): 13 The rates of loss of O6-methylguanine (I) [20535-83-5] and O6-ethylguanine (II) [51866-19-4] from rat liver DNA were detd. 15 min-4 h after various doses (5 mg/kg to 2 mg/kg) of dimethylnitrosamine [62-75-9] and diethylnitrosamine [55-18-5] which produced total amts. of these adducts in the range of 300-16,000 mols./cell. This amt. is considerably less than the content of O6-alkylguanine-DNA alkyltransferase (III) [92767-51-6] protein (~60,000 mols./hepatocyte). The adducts were lost with pseudo-1st order kinetics. The half-life for I was 47 min. II was removed 3.6-fold more slowly with a half-life of 172 min. The ability of partially purified rat liver III to remove I and II from [3H]alkyl-labeled DNA substrates in vitro was measured; I was removed 3.4-fold more rapidly than was II. Apparently most, if not all, of the repair of these adducts which occurs within the 1st 4 h after treatment is due to III. Diethylnitrosamine, which is slightly more potent as a carcinogen to rat liver, produced a total amt. of II of 3.7 mmol/mol guanine/mg, compared to I (28 mmol/mol guanine/mg) given by dimethylnitrosamine. The slower rate of loss of the Et adduct is not sufficient to account for this difference; other DNA adducts (possibly O-alkylpyrimidines) may contribute to the initiation of tumors by diethylnitrosamine. Preliminary evidence that the rat liver III can also remove hydroxyethyl groups from DNA at a rate slower than removal of Et groups was also obtained. Bacterial III removed Me, Et, and hydroxyethyl groups from the O6 position of guanine in DNA. The bacterial protein removed Me groups very rapidly but was much slower than the rat liver protein on the larger adducts. The relative rates of repair of different alkyl groups may be species specific and must be detd. exptl. before conclusions concerning biol. effects can be drawn.