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

本文观察了二氧化氮（NO_2）对N-二（2-羟丙基）亚硝胺（DHPN）诱发大鼠肺肿瘤的影响。在6周龄时一次性腹腔注射0.5g DHPN/kg体重或生理盐水，然后暴露于清洁空气、0.04ppm或4ppm NO中17个月。DHPN +4ppmNO_2组大鼠肺肿瘤发生率为13%，肿瘤类型为腺瘤和腺癌，其中腺瘤4/40（10%），腺癌1/40（3%），而DHPN +清洁空气组和DHPN +0.04ppmNO_2组大鼠肺肿瘤发生率仅为3%（1/40）。分别肿瘤均为腺瘤。DHPN +清洁空气组与DHPN +4ppmNO_2组肿瘤发生率无显著性差异。DHPN +0.4ppm组和各NO_2暴露组均未发现肺肿瘤。在注射DHPN的大鼠肺中，肺泡细胞增生发生率最高。而增生率与NO_2暴露浓度无相关性。DHPN +4ppmNO_2组有17只（43%）大鼠出现支气管粘膜增生，而DHPN处理后的清洁空气组、0.04ppmNO_2组和0.4ppmNO_2组各有1只（3%）大鼠出现支气管粘膜增生。4ppmNO_2暴露组大鼠肺组织增生较4ppmNO_2暴露组轻，提示4ppmNO_2暴露可促进亚致癌剂量DHPN大鼠肺肿瘤的发生。低浓度NO_2对Wistar大鼠肺肿瘤生长无明显影响。

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.