報告書番号

U98039

タイトル（和文）

商用周波磁界の変異原性および助変異原性におよぼす影響 -－サルモネラ菌および大腸菌を用いた微生物変異原性試験による評価－-

タイトル（英文）

Exposure to a 50Hz, 14mT circularly polarized magnetic field has no detectable mutagenic and co-mutagenic potential-Estimation by microbial mutation assay using Salmonella typhimurium and Escherichia coli as tester strains-

概要 （図表や脚注は「報告書全文」に掲載しております）

商用周波磁界の遺伝子変異に与える影響について微生物変異原性試験法を用い検討した。サルモネラ菌TA1535、TA1537、TA98、TA100および大腸菌WP2 uvrA、WP2 uvrA/pKM101を用い、50Hz、14mTrmsの回転円磁界を48時間曝露した。また、同様の磁界曝露条件のもとで、化学変異原の変異原性に与える影響（助変異原性）も検討した。化学変異原としてDNA反応性の変異原３種、代謝活性化によりDNA反応性となる変異原、塩基アナログ、フレームシフト型変異原、ラジカル変異原二種を用いた。いずれの場合も、磁界曝露による、復帰変異コロニー数に統計的に有為でかつ再現性のある変化は見られなかった。このことから、14mT以下の商用周波磁界は、直接および間接的に遺伝子に作用し変異を起こす可能性が極めて低いことが示された。

概要 （英文）

Some reports show the strong static and power frequency magnetic fields (MFs) act as mutagen or enhance the mutagenicity of chemical mutagens (co-mutagenicity). The aims of this study were to evaluate the mutagenicity of 50Hz, 14mTrms circularly polarized MF, and also to evaluate the effect of the MF on co-mutagenicity for various chemical mutagens including hydroxyl radical, using alternative Ames test. A wide-range exposure system was used for generating 50Hz sinusoidal and circularly polarized magnetic field. Chemical mutagens were used as following; N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG), 2-(2-fulyl)-3-(5-nitro-2-furyl)acrylamide (AF-2) and 4-nitro-quinoline-Nﾕ-oxide (4-NQO) as DNA reactive reagents; 2-aminoanthracene (2AA) as a DNA reactive promutagen which activated metabolically by rat S9mix; N4-aminocytidine(AC) as a base analog; and cumen hydroperoxide (CH) and t-butyl hydroperoxide (BH) as a source of hydroxyl radical. Test strains were Salmonella typhimurium TA1535, TA1537, TA98 and TA100 (histidine-biotin auxotroph), and Escherichia coli WP2 uvrA and WP2 uvrA/pKM101 (tryptophan auxotroph). In the test, five types of mutation could be detected by using these strains. Base substitution could be detected in TA100, TA1535, WP2 uvrA and WP2 uvrA/ pKM101. The frame shift could be detected in TA98 and TA1537. By exposure to 50Hz, 14mT circularly polarized MF for 48h, the number of prototroph mutant colonies did not increase. This result shows that only exposure to the MF could not induce mutagenesis of the test strains. In the same way, statistically no significant difference was also observed on the number of prototroph mutant colonies induced by each chemical mutagen between the MF exposure and the sham exposure groups. This result shows the mutagenicity of the chemical mutagens was not affected by the MF exposure. It is inferred that (1) membrane permeability, (2) metabolization of mutagen in cells, (3) reaction between DNA and chemicals, and (4) the DNA repair processes are not affected by the MF exposure. The result also suggests that the MF could not affect on the radical reaction with DNA because the mutagenicity of BH and CH was not affected by the MF exposure. In the case of 2AA, the result suggests that the MF exposure could not affect on electron transfer reaction between the chemical and S9mix. In conclusion, the exposure to power frequency circularly polarized MF below an intensity of 14mT could not show any mutagenicity and any effect on co-mutagenicity for various chemical mutagens including radical species.

報告者

キーワード