報告書番号

U99010

タイトル（和文）

ヒト白血病由来細胞（HL60細胞）のチロシンのリン酸化に対する50Hz磁界の影響

タイトル（英文）

Effect of 50Hz magnetic fields on tyrosine phosphorylation in HL60 cells

概要 （図表や脚注は「報告書全文」に掲載しております）

50Hz、14.1mTrmsの回転円磁界をHL60細胞に1、8、16、24の各時間で曝露しウエスタン-イムノブロット分析を用いてチロシンキナーゼのチロシンのリン酸化について分析した結果、1時間の曝露でチロシンのリン酸化に再現性のある上昇が観察された。このため、14.1mTrmsの磁界曝露により影響が観察された曝露1時間で、1.41mTrmsおよび0.14mTrmsの磁界強度で曝露を行って同様に分析をしたが、1.41mTrms、0.14mTrmsでは、変化が観察されなかった。今回の結果から、社会生活で曝露される磁界強度の約10000倍程度の磁界で、HL60細胞のチロシンキナーゼのチロシンのリン酸化に短時間での変化が示唆されたが、それ以下の強度では全く変化が観察されなかった。

概要 （英文）

Epidemiological studies suggest slight increase in the incidence of cancer (for example, brain cancer and childhood leukemia) due to exposure to low frequency magnetic fields (MFs). On the cellular level, experimental studies using molecular biological technique demonstrated many phenomena of scientific probability about the effects of MFs. Especially, Goodman and colleague(1989) reported the effect of magnetic fields on c-myc transcription in HL60 cells that is a human leukemia origin cell．However, Other investigators such as Lacy-Hulbert et al.(1995) and Saffer et al.(1995) could not replicate the result, and reliability of their results is a target of a big interest. On the other hand, tyrosine phosphorylation is a good marker to study the effect of magnetic fields in the wide area of biological response and early process of the signal transduction. Therefore, we investigated the effect of circularly polarized 50Hz MFs on intracellular tyrosine phosphorylation by tyrosine kinases in HL60 cells. We employed two Merritt-coil exposure systems. One was the wide-range exposure system which could produce maximum 10mT (horizontally and vertically, each), 14.1mTrms (circularly polarized) MFs at sinusoidal 50 Hz. The other was the low-level exposure system which could produce maximum 0.5mTrms (horizontally and vertically, each) and 0.7mTrms (circularly polarized) MFs at sinusoidal 50 Hz. HL60 cells were cultured in vented culture flask under 37℃, 5% CO2 and >95% humidity, and were exposed to 14.1mTrms for 1, 8,16 and 24 hr, intracellular tyrosine phosphorylation analyzed by Western immuno-blotting and Enhanced Chemi-Luminescence (ECL) analysis. We detected enhancement of tyrosine phosphorylation under 14.1mTrms MFs exposure for 1hr. On the other hand, in the cases of 8,16 and 24 hr MFs exposure, we did not detect any enhancement of tyrosine phosphorylation. These results suggested that tyrosine kinases were affected by relatively short time (1hr) MFs exposure.Under longer time (8,16 and 24hr) MFs exposure, there is a possibility that the signal about tyrosine phosphorylation by tyrosine kinases was changed to other signal transduction cascade such as serine or threonine phosphorylation. We investigated the cases of 1.41 and 0.14mTrms MFs exposure for 1hr and analyzed by the same manner of 14.1mTrms on purpose that we detect the dose response of tyrosine phosphorylation to MFs exposure. Under these two conditions, we did not detect any enhancement of tyrosine phosphorylation. These results suggested that effects of MFs on tyrosine phosphorylation were detected only under 14.1mTrms, and 1.41 and 0.14mTrms exposure did not effect the tyrosine phosphorylation.

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