Nomura T, Hayashi T, Masuyama T, Tanaka S, Nakajima H, Kurokawa N, Isa Y
Department of Radiation Biology, Osaka University.
Jpn J Cancer Res. 1990 Aug;81(8):742-6. doi: 10.1111/j.1349-7006.1990.tb02639.x.
The carcinogenicity of sublimed urethane (ethyl carbamate) in air was examined with mice. JCL:ICR mice were nursed in a plastic cage inside a vinyl chamber which was ventilated 4 times per hour. The mice were exposed to urethane gas for various periods by passing air which contained a high concentration of sublimed urethane (1.29 micrograms/ml) into the vinyl chamber, or by placing a vessel containing crystalline urethane inside the vinyl chamber so that it was filled with spontaneously-sublimed urethane gas at a low concentration (0.25 microgram/ml). When female mice were killed 5 months after exposure, lung tumor frequency increased almost linearly with the number of days of exposure in the low concentration experiment, but increased in a non-linear manner in the high concentration experiment. In terms of nearly the same total dose, i.e., (concentration of urethane gas in air) X (days of inhalation), one day of exposure to urethane gas at the low concentration induced lung tumors at a significantly higher frequency than 1/4 day of exposure to urethane gas at the high concentration. When male mice were killed at 12 months after exposure to examine the progressive change of induced tumors, malignant, invasive and metastatic tumors were found to have been induced more frequently in the lung after exposure to urethane gas at the low concentration (0.25 microgram/ml for 10 days) than at the high concentration (1.29 microgram/ml for 4 days), although the total dose in the former group was about half of that in the latter. Continuous exposure to urethane gas for a longer period at the low concentration seems to be more efficient for the induction, promotion and/or progression of lung tumors than the exposure for a shorter period at the high concentration.
用小鼠研究了升华尿烷（氨基甲酸乙酯）在空气中的致癌性。日本实验动物中央研究所（JCL）的ICR小鼠饲养在乙烯基实验室内的塑料笼中，该实验室每小时通风4次。通过将含有高浓度升华尿烷（1.29微克/毫升）的空气通入乙烯基实验室，或在乙烯基实验室内放置一个装有结晶尿烷的容器，使其充满低浓度（0.25微克/毫升）的自发升华尿烷气体，让小鼠在不同时间段暴露于尿烷气体中。当雌性小鼠在暴露5个月后处死时，在低浓度实验中，肺肿瘤发生率几乎随暴露天数呈线性增加，但在高浓度实验中呈非线性增加。就几乎相同的总剂量而言，即（空气中尿烷气体浓度）×（吸入天数），低浓度下一天暴露于尿烷气体诱发肺肿瘤的频率明显高于高浓度下1/4天暴露于尿烷气体的频率。当雄性小鼠在暴露12个月后处死以检查诱发肿瘤的进展变化时，发现低浓度（0.25微克/毫升，暴露10天）暴露于尿烷气体后，肺中诱发恶性、侵袭性和转移性肿瘤的频率高于高浓度（1.29微克/毫升，暴露4天），尽管前一组的总剂量约为后一组的一半。低浓度下长时间持续暴露于尿烷气体似乎比高浓度下短时间暴露对肺肿瘤的诱发、促进和/或进展更有效。
