この研究は、肝がんの実験的発症モデルにおける前がん病変の成長に対する4.5 mT - 120 Hz の超低周波磁界（ELF-EMF）の影響を調べた。雄のFischer-344を“改変型耐性肝細胞モデル（MRHM）”に仕立て、そのモデルでの肝がん発症・アポトーシス・増殖･細胞周期進行に対するELF-EMFの影響を組織化学的なTUNELアッセイ・カスパーゼ3レベル・ウェスタンブロット分析などで測定した。すなわち、化学物質投与によるイニシェーションとその後に部分肝切除を施された MRHMでは、変化した肝細胞の急速な増殖が誘導され、肝臓の前がん病変が形成されるので、この過程における影響を調べたものである。無処置で無ばく露のNC群、MRHM処置+ELF-EMF擬似ばく露のCT群、MRHM処置+ELF-EMFばく露のCTF群を比較した。その結果、CTF群では前がん病変の数と面積が50％以上低下した；TUNEL試験陽性細胞の数および開裂カスパーゼ3レベルに影響はなかった；増殖期細胞核抗原Ki-67およびサイクリンD1の発現は、CT群に比べCTF群で有意に低下した、などELF-EMFばく露により前がん病変増殖の抑制が示されたと報告している。
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The aim of this study was to use the "modified resistant hepatocyte model", which induces a rapid proliferation of altered hepatocytes to form preneoplastic lesions in the rat liver, to seek information concerning the effects of extremely low frequency electromagnetic fields on hepatocarcinogenesis (carcinogenesis in the liver).
The authors hypothesized that the development of preneoplastic lesions chemically induced in rat livers could be affected by extremely low frequency electromagnetic field exposure (4.5 mT, 120 Hz). The extremely low frequency electromagnetic field was applied from 7 days before starting the carcinogenic treatment, because the initial approach of the experiment was to assess the electromagnetic field effect on the inhibition of preneoplastic lesions development in rat liver (to prevent the disease in the early stages of its development).
Carcinogenesis was initiated by diethylnitrosamine. Seven days later the animals were treated by 2-acetylaminofluorene for three consecutive days (before a partial hepatectomy). Three groups of 6 rats each were used: 1) control group (no treatment), 2) sham exposed positive control group (carcinogenic treatment and sham exposure), 3) exposed group (carcinogenic treatment and exposure). The animals were sacrificed on day 25 after carcinogenesis initiation.
ばく露時間: continuous for 50 min/day on 32 days
|ばく露時間||continuous for 50 min/day on 32 days|
|ばく露装置の詳細||solenoid with a diameter of 25 cm and 1900 turns of AWG 20-gauge copper-enameled magnetic wire in two layers; rats placed in the center of the coil in a 16 cm x 16 cm x 25 cm Plexiglas cage|
|Sham exposure||A sham exposure was conducted.|
The application of the extremely low frequency electromagnetic field resulted in a decrease of more than 50% of the number and the area of gamma-glutamyltransferase-positive preneoplastic lesions and glutathione S-transferase-p expression. The number of positive cells in the TUNEL assay and the caspase 3 levels were unaffected. However, the expressions of PCNA, Ki-67, and cyclin D1 expression decreased significantly, as compared to the sham exposed group.
The authors conclude that the application of 120 Hz extremely low frequency electromagnetic field (4.5 mT) inhibits preneoplastic lesions chemically induced in the rat liver through the reduction of cell proliferation, without altering the apoptosis process. This finding could be the basis for the design of strategies and clinical applications of extremely low frequency electromagnetic fields to treat hepatocellular carcinoma.