Löscher W, Mevissen M, Lehmacher W, Stamm A
Department of Pharmacology, Toxicology and Pharmacy, School of Veterinary Medicine, Hannover, Germany.
Cancer Lett. 1993 Jul 30;71(1-3):75-81. doi: 10.1016/0304-3835(93)90100-n.
In view of the methodological problems of epidemiological studies on associations between exposures to 50/60 Hz magnetic fields (MF) and increased incidence of cancers, laboratory studies are necessary to determine if 50/60 Hz MF are cancer promoters or can progress cancers. The objective of the present study was to determine if an alternating MF of low flux density exerts tumor-promoting or co-promoting effects in a model of breast cancer in female rats. Mammary tumors were induced by the chemical carcinogen 7,12-dimethylbenz(a)anthracene (DMBA). A group of 99 rats was exposed to a homogeneous MF of 50 Hz, 100 microT (microtesla), for 24 h/day 7 day/week for a period of 91 days; another group of 99 rats was sham-exposed under the same environmental conditions as the MF-exposed rats. The exposure chambers were identical for MF-exposed and sham-exposed animals. DMBA was administered orally at a dose of 5 mg/kg at the first day of exposure and at weekly intervals thereafter up to a total dose of 20 mg per rat. The animals were palpated once weekly to assess the development of mammary tumors. In controls, DMBA induced tumors in about 40% of the animals within three months of first application. Eight weeks after DMBA application the MF-exposed rats exhibited significantly more tumors than sham-exposed animals. This difference in the rate of tumor development was observed throughout the period of exposure. At the end of the three-month period of MF exposure the tumor incidence in MF-exposed rats was 50% higher than in sham-exposed rats, the difference being statistically significant. Furthermore, the size of tumors as estimated by palpation was significantly larger in the MF-exposed compared to sham-exposed rats. The data demonstrates that long-term exposure of DMBA-treated female rats to an alternating MF of low flux density promotes the growth and increases the incidence of mammary tumors, thus strongly indicating that MF exposure exerts tumor-promoting and/or copromoting effects.
鉴于关于暴露于50/60赫兹磁场（MF）与癌症发病率增加之间关联的流行病学研究存在方法学问题，有必要进行实验室研究以确定50/60赫兹MF是否为癌症促进剂或能否促使癌症进展。本研究的目的是确定低通量密度的交变MF在雌性大鼠乳腺癌模型中是否具有促肿瘤或协同促肿瘤作用。通过化学致癌物7,12 - 二甲基苯并(a)蒽（DMBA）诱导乳腺肿瘤。一组99只大鼠每天24小时、每周7天暴露于50赫兹、100微特斯拉（μT）的均匀MF中，持续91天；另一组99只大鼠在与MF暴露组相同的环境条件下进行假暴露。MF暴露组和假暴露组的动物暴露室相同。在暴露的第一天口服给予DMBA，剂量为5毫克/千克，此后每周一次，直至每只大鼠的总剂量达到20毫克。每周对动物进行一次触诊以评估乳腺肿瘤的发展情况。在对照组中，首次应用DMBA后三个月内约40%的动物诱发了肿瘤。DMBA应用八周后，MF暴露组大鼠的肿瘤明显多于假暴露组动物。在整个暴露期间都观察到了肿瘤发展速度的这种差异。在MF暴露三个月结束时，MF暴露组大鼠的肿瘤发生率比假暴露组大鼠高50%，差异具有统计学意义。此外，通过触诊估计，MF暴露组大鼠的肿瘤大小明显大于假暴露组大鼠。数据表明，长期将经DMBA处理的雌性大鼠暴露于低通量密度的交变MF可促进乳腺肿瘤的生长并增加其发生率，从而有力地表明MF暴露具有促肿瘤和/或协同促肿瘤作用。
