Study on proportional effect of life span exposure of air pollutant (NO_2) on respiratory tumor carcinogenesis.

研究了二氧化氮（NO_2）对雄性Wistar大鼠n -双（2-羟丙基）亚硝胺（DHPN）致肺肿瘤的影响。6周龄大鼠一次性腹腔注射每公斤体重0.5 g DHPN或生理盐水，然后暴露于0.04 ppm或4 ppm NO的洁净空气中17个月。DHPN + 4 ppm NO_2组大鼠肺肿瘤发生率为13%，肿瘤类型为腺瘤和腺癌。40只大鼠中4只出现腺瘤（10%），1只出现腺癌（3%）。DHPN +清洁空气组和DHPN + 0.04 ppm NO_2组大鼠肺肿瘤发生率仅为3%（1/40）。肿瘤为腺瘤。DHPN +清洁空气组与DHPN + 4 ppm NO_2组肿瘤发生率无显著性差异。DHPN + 0.4 ppm组和no_2暴露组均未见肺肿瘤。肺泡细胞增生发生率最高的是。注射DHPN的大鼠肺。但不同浓度的NO_2对细胞增生的影响不显著。DHPN + 4ppm NO_2处理组17只（43%）大鼠出现细支气管黏膜增生，在0.04 ppm和0.4 ppm NO_2处理组40只大鼠中有1只（3%）出现细支气管黏膜增生。4 ppm NO_2未加DHPN处理的大鼠肺组织增生较4 ppm NO_2加DHPN处理组轻。结果表明，4 ppm NO_2可促进亚致癌剂量DHPN大鼠肺肿瘤的发展。然而，低浓度NO_2对Wistar大鼠肺肿瘤的发展没有影响。

The effects of nitrogen dioxide (NO_2) on lung tumorigenesis by N-bis(2-hydroxypropyl) nitrosamine (DHPN) in male Wistar rats Were investigated. Rats were injected with o.5 g DHPN per kg body weight or saline intraperitoneally one time at 6 weeks of age, and then exposed to clean air, 0.04 ppm or 4 ppm NO for 17 months. Incidence of tumor in lungs of rats in DHPN + 4 ppm NO_2, group was 13%, and the tumors were adenoma and adenocarcinoma.Adenoma was seen in 4 of 40 rats (10%) and adenocarcinoma was seen in I of 40 rats (3%).The incidence of tumor in lungs of rats in DHPN + clean air and DHPN + 0.04 ppm NO_2 groups was only 3% (1/40), respectively. The tumors were adenoma. There was no significant difference in the incidence of tumors between DHPN + clean air group and DHPN + 4 ppm NO_2 group. No lung tumor was seen in DHPN + 0.4 ppm group and each NO_2-exposed group without DHPN treatment. Alveolar cell hyperplasia occurred at the highest incidence in.lungs of rats injected with DHPN. But, there was no any correlation between the incidence of hyperplasia and each concentration of NO_2 exposed. Bronchiole mucosal hyperplasia was seen in 17 of rats (43%) in the DHPN + 4 ppm NO_2 group, and in I of 40 rats (3%) in the each clean air, 0.04 ppm or 0.4 ppm NO_2 exposed-groups with DHPN treatment. The hyper- plasia in lungs of rats exposed to 4 ppm NO_2 without DHPN treatment was more slighter than that seen in the 4 ppm NO_2-exposed group with DHPN treatment.These results indicate that development of lung tumors in rats injected with subcarcino- genic dose of DHPN was-enhanced by exposure to 4 ppm NO_2. However, low levels of NO_2 effect on lung tumor development was not observed in Wistar rats.