Glycidyl methaerylate (GMA) is a recently recognized chemical mutagen. In order to explore the mutagenicity and mutagenic process of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, and restriction...Glycidyl methaerylate (GMA) is a recently recognized chemical mutagen. In order to explore the mutagenicity and mutagenic process of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, and restriction enzyme mapping. The binding between GMA and DNA in vitro has been verified by means of a spectrophotometric method. When pBR322 and GMAbound pBR322 were used to transform Eschenchia coli HB101, the following results were obtained: (1) The transformation efficiency of GMA-bound pBR322 was much lower than that of pBR322 alone. (2) GMA-bound pBR322 induced phenotype changes in competent cells (i.e., tetracycline-resistance inactivation or ampicillin-resistance inactivation). There were two mutants of pBR322, Ap~RTc~S and Ap~STc~R, in the transformants and a deductive mutant Ap~STc~S in the nontranstormants. (3) All of the selected mutants were stable and heritable. (4) When restriction enzyme maps were used to analyze the mutant Ap~RTc~S, four of seven maps were changed. some sites were shifted to other resistant gene regions, for example, sites of Bgll, EcoRl, Ilindlll. Hinclll, etc., and there was a new recognition site for Hindi (252). We did not observe any DNA fragment insertion or deletion on any maps. Our results suggest that when GMA is covalently linked to the plasmid DNA, it gives rise to a premutagenic lesion of DNA that is converted in vivo into a point mutation. (C)1990 Academic Press, Inc.展开更多
In in vivo test, rats were orally administrated with glycidyl methacrylate (GMA) at respective doses of 250 mg/kg, 125 mg/kg and 62. 5 mg/kg, 31. 25 mg/kg and solvent as control for 14 days. DNA adducts produced in t...In in vivo test, rats were orally administrated with glycidyl methacrylate (GMA) at respective doses of 250 mg/kg, 125 mg/kg and 62. 5 mg/kg, 31. 25 mg/kg and solvent as control for 14 days. DNA adducts produced in the liver, kidney, blood and testis were analyzed by RP-HPLC and nuclease P1 mediated 32 P-postlabelling method. Results showed that several potential GMA-DNA adducts were formed in various organs (4 adducts in blood, 3 adducts in liver and kidney, 1 adduct in testis). A linear dose-response relationship was observed within certain dose levels. The relative adduct labeling values failed to further increase any more when the concentration went up to 125 mg/kg. The order of adduct level with GMA was kidney, liver, blood and testis. The GMA adduct N3methacrylate-2-hydroxypropyl-dCMP was found in kidney, liver and blood. These results indicated that GMA could react with negatively charged centers on DNA and form GMA-DNA adducts. If carcinogerrinduced DNA damage exceeds the ability of repair systems, gene mutation is induced.Therefore, study on molecular mechanism of gene mutation induced by DNA adducts is not only an important part of chemical-carcinogenesis, but also provides information on critical biomarkers for monitoring human exposure to genetic toxins.展开更多
文摘Glycidyl methaerylate (GMA) is a recently recognized chemical mutagen. In order to explore the mutagenicity and mutagenic process of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, and restriction enzyme mapping. The binding between GMA and DNA in vitro has been verified by means of a spectrophotometric method. When pBR322 and GMAbound pBR322 were used to transform Eschenchia coli HB101, the following results were obtained: (1) The transformation efficiency of GMA-bound pBR322 was much lower than that of pBR322 alone. (2) GMA-bound pBR322 induced phenotype changes in competent cells (i.e., tetracycline-resistance inactivation or ampicillin-resistance inactivation). There were two mutants of pBR322, Ap~RTc~S and Ap~STc~R, in the transformants and a deductive mutant Ap~STc~S in the nontranstormants. (3) All of the selected mutants were stable and heritable. (4) When restriction enzyme maps were used to analyze the mutant Ap~RTc~S, four of seven maps were changed. some sites were shifted to other resistant gene regions, for example, sites of Bgll, EcoRl, Ilindlll. Hinclll, etc., and there was a new recognition site for Hindi (252). We did not observe any DNA fragment insertion or deletion on any maps. Our results suggest that when GMA is covalently linked to the plasmid DNA, it gives rise to a premutagenic lesion of DNA that is converted in vivo into a point mutation. (C)1990 Academic Press, Inc.
文摘In in vivo test, rats were orally administrated with glycidyl methacrylate (GMA) at respective doses of 250 mg/kg, 125 mg/kg and 62. 5 mg/kg, 31. 25 mg/kg and solvent as control for 14 days. DNA adducts produced in the liver, kidney, blood and testis were analyzed by RP-HPLC and nuclease P1 mediated 32 P-postlabelling method. Results showed that several potential GMA-DNA adducts were formed in various organs (4 adducts in blood, 3 adducts in liver and kidney, 1 adduct in testis). A linear dose-response relationship was observed within certain dose levels. The relative adduct labeling values failed to further increase any more when the concentration went up to 125 mg/kg. The order of adduct level with GMA was kidney, liver, blood and testis. The GMA adduct N3methacrylate-2-hydroxypropyl-dCMP was found in kidney, liver and blood. These results indicated that GMA could react with negatively charged centers on DNA and form GMA-DNA adducts. If carcinogerrinduced DNA damage exceeds the ability of repair systems, gene mutation is induced.Therefore, study on molecular mechanism of gene mutation induced by DNA adducts is not only an important part of chemical-carcinogenesis, but also provides information on critical biomarkers for monitoring human exposure to genetic toxins.
