Effects of chrysotile asbestos on lung and pleural carcinogenesis of N-bis(2-hydroxypropyl)nitrosamine in rats

Our plain-English summary of Effects of chrysotile asbestos on lung and pleural carcinogenesis of N-bis(2-hydroxypropyl)nitrosamine in rats, by H. Katada, R. Higashiguchi, H. Maruyama, et al (Cancer Letters, 1983).

The study

• Authors: H. Katada, R. Higashiguchi, H. Maruyama, Y. Emi, Y. Yokose, S. Takahashi, R. Mikami, Y. Konishi
• Journal: Cancer Letters
• Published: 1983;17(3):313-20
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The effects of chrysotile asbestos on lung and pleural carcinogenesis by N-bis(2-hydroxypropyl)nitrosamine (DHPN) in male Wistar rats were studied. Chrysotile, 30 mg per rat, was injected into the left pleural cavity and 3 g/kg body wt. DHPN was injected once into the abdominal cavity. Lung tumors (adenoma, adenocarcinoma, squamous cell carcinoma, and combined carcinoma) occurred at the highest incidence (100%). Adenocarcinoma was seen in 4 of 11 (36%) rats killed at 35 weeks and in 6 of 12 (50%) rats killed at 52 weeks, squamous cell carcinoma occurred in 1 of 11 (9%) rats killed at 35 weeks and 3 of 12 (25%) rats killed at 52 weeks, and mixed carcinoma was seen in 1 of 12 (8%) rats killed at 52 weeks, which received chrysotile and DHPN. Adenocarcinoma was seen in 9 of 11 (82%) rats which received DHPN only and killed at 52 weeks. Mesotheliomas were seen in 2 of 11 (18%) rats, killed at 35 weeks, and 3 of 12 (25%) rats, killed at 52 weeks, which received chrysotile and DHPN. Hyaline thickening of the pleura was seen in 100% of rats receiving chrysotile. Mesothelial cell hyperplasia and adenomatous and/or fibromatous growth of the mesothelium were seen in the pleura on both sides, ranging from 36% to 50% and 31% to 64% in rats receiving chrysotile and DHPN, respectively. Asbestos bodies were seen in the pleura on both sides and in the lung.

In plain English

This was an animal experiment in male Wistar rats (62 per the methods, though the table's counts disagree). The authors studied how chrysotile asbestos, injected twice (15 mg each) into the left chest (pleural) cavity, affected lung and pleural tumor development in rats also given one abdominal injection of a chemical carcinogen, DHPN. Mesothelioma occurred only in rats given both: 2 of 11 killed at 35 weeks and 3 of 12 killed at 52 weeks. None occurred with chrysotile or DHPN alone. All rats killed at 52 weeks in the chrysotile-plus-DHPN and DHPN-only groups had lung tumors. Adenocarcinoma was seen in 6 of 12 combined-treatment rats at 52 weeks versus 9 of 11 DHPN-only rats. Squamous cell and mixed carcinomas appeared only in the combined group. Every chrysotile-treated rat had hyaline thickening of the pleura. Pleural changes appeared on both sides, although asbestos was injected only on the left. The authors wrote that their results suggested a synergistic effect of asbestos and DHPN in producing mesothelioma. They suggested the small fibers and the experimental period might explain the low mesothelioma rate.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Animal experiment; rats were given chrysotile into the pleural cavity and/or a single injection of the chemical carcinogen DHPN, then killed at 35 or 52 weeks and examined at autopsy
• Who was studied: Male Wistar rats from Clea Japan Inc., divided into four groups: saline control, chrysotile only, chrysotile plus DHPN, and DHPN only. The methods state 62 rats, but Table 1's final counts (17, 13, 11 + 12, 8 + 11) add to 72, so the total cannot be confirmed from this text.
• Exposure: Chrysotile asbestos given as two intrapleural (into the chest cavity) injections of 15 mg, one week apart. Group 2 received chrysotile alone. Group 3 received chrysotile with a single intraperitoneal (abdominal) injection of 3 g/kg body weight of the nitrosamine DHPN. Comparison groups received saline or DHPN alone.
• Main results:
  • In rats given chrysotile plus DHPN, mesothelioma occurred in 2 of 11 (18%) killed at 35 weeks and 3 of 12 (25%) killed at 52 weeks
  • Mesotheliomas developed only in the chrysotile-plus-DHPN group (Group 3), not in rats given chrysotile alone (Group 2)
  • Total lung tumors were found in 100% of rats killed at 52 weeks in both the chrysotile-plus-DHPN group and the DHPN-only group
  • Lung adenocarcinoma in the chrysotile-plus-DHPN group: 4 of 11 (36%) rats killed at 35 weeks and 6 of 12 (50%) rats killed at 52 weeks
  • Lung adenocarcinoma in the DHPN-only group: 9 of 11 (82%) rats killed at 52 weeks
  • Squamous cell carcinoma (1 rat at 35 weeks, 3 rats at 52 weeks) and mixed carcinoma (1 rat at 52 weeks) occurred only in the chrysotile-plus-DHPN group, not in the DHPN-only group
  • Hyaline thickening of the pleura was found in 100% of rats given chrysotile
  • Mesothelial cell hyperplasia and adenomatous and/or fibromatous growth of the mesothelium were seen in the two chrysotile groups (Groups 2 and 3). Their incidences ranged from 18% to 50% and from 8% to 64% respectively, counting left and right pleura separately.
  • Pleural changes appeared on both sides of the chest even though chrysotile was injected only into the left pleural cavity
  • In chrysotile-plus-DHPN rats killed at 52 weeks, adenomatous and/or fibromatous growth of the mesothelium was more frequent in the left pleura than the right (p between 0.02 and 0.05)
  • Asbestos bodies were found in the pleura on both sides and in the lung
• The authors' conclusion: The authors wrote that their results suggested two things: chrysotile affected DHPN lung carcinogenesis, as shown by the production of squamous cell and combined carcinomas, and a synergistic effect of asbestos and DHPN resulted in mesothelioma.
• Limitations the authors state:
  • The authors stated that the effects of chrysotile combined with a lower dose of DHPN still need study
  • The authors suggested that the low mesothelioma incidence may reflect the small chrysotile fibers used and the length of the experiment
  • The authors said that whether the mesothelial lesions are precursors of mesothelioma requires further sequential analysis

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Lung cancer.

Medical terms in this study, explained in our Lexicon: Chrysotile, Carcinogenesis, Pleural Cavity, Adenocarcinoma, Squamous Cell Carcinoma, Carcinoma, Mesothelioma, Pleura.

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• Exposure to nitrosamines, carbon black, asbestos, and talc and mortality from stomach, lung, and laryngeal cancer in a cohort of rubber workers — K. Straif, U. Keil, et al. (2000)
• Lung proliferative and clearance responses to inhaled para-aramid RFP in exposed hamsters and rats: comparisons with chrysotile asbestos fibers — D.B. Warheit, S.I. Snajdr, et al. (1997)
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