Beniashvili D S, Bulanishvili V G, Menabde M Z, Gupta D, Anisimov V N
Center for Oncology Research of the Ministry of Health, Tübingen University, Germany.
Vopr Onkol. 1993;39(1-3):52-60.
Female rats aged I month and older were kept indoors in darkness, under lighting for 24 hours or exposed to ordinary lighting (light--12 hrs; darkness--12 hrs). Three weeks after the beginning of the experiment, they received N-nitrosomethyl urea (NMU) treatment in the dose of 50 mg/kg, intravenously, at weekly intervals, and were exposed to alternating 50 Hz (AMF) or static 0.2 oersted, (DMF) electromagnetic field radiation for 3 hrs, daily. Under usual lighting conditions, NMU treatment was followed by the development of mammary gland adenocarcinoma (MGA) in 31% of the animals. However, AMF or DMF treatment was followed by a shorter period of latency, without affecting MGA frequency. Constant lighting was found to stimulate a sharp increase in carcinogenesis: MGA frequency in groups receiving NMU, NMU+AMF or NMU+DMF was 57, 81 and 61%, respectively; latency period dropped by half as compared with usual lighting conditions. Conversely, the rats constantly kept in darkness revealed significant inhibition of mammary gland carcinogenesis, MGA frequency in NMU, NMU+AMF or NMU+DMF groups being 3, 4 and 2%, respectively. A blood serum--hormone assay showed constant lighting to decrease melatonin level and to increase prolactin concentration for all the modalities of carcinogenic treatment used. The results point to a significant promoting effect of constant lighting on mammary gland carcinogenesis by NMU in rats. This effect is potentiated by additional AMF or DMF treatment. Conversely, constant darkness inhibits mammary gland carcinogenesis and mitigates the pernicious effect of low-frequency electro-magnetic radiation.
1月龄及以上的雌性大鼠被饲养在室内黑暗环境中，或接受24小时光照，或暴露于普通光照下（光照12小时；黑暗12小时）。实验开始三周后，它们每周静脉注射一次剂量为50毫克/千克的N-亚硝基甲基脲（NMU），并每天暴露于50赫兹交变（AMF）或0.2奥斯特静态（DMF）电磁场辐射下3小时。在通常的光照条件下，NMU处理后31%的动物发生了乳腺腺癌（MGA）。然而，AMF或DMF处理后潜伏期缩短，且不影响MGA发生率。发现持续光照会刺激致癌作用急剧增加：接受NMU、NMU + AMF或NMU + DMF处理的组中MGA发生率分别为57%、81%和61%；与通常光照条件相比，潜伏期缩短了一半。相反，持续处于黑暗中的大鼠显示出乳腺致癌作用受到显著抑制，NMU、NMU + AMF或NMU + DMF组中的MGA发生率分别为3%、4%和2%。血清激素检测显示，对于所有使用的致癌处理方式，持续光照都会降低褪黑素水平并增加催乳素浓度。结果表明，持续光照对大鼠中NMU诱导的乳腺致癌作用具有显著的促进作用。额外的AMF或DMF处理会增强这种作用。相反，持续黑暗会抑制乳腺致癌作用，并减轻低频电磁辐射的有害影响。
