Experimentally induced mesothelioma in white rats in response to intraperitoneal administration of amorphous crocidolite asbestos: preliminary report

Our plain-English summary of Experimentally induced mesothelioma in white rats in response to intraperitoneal administration of amorphous crocidolite asbestos: preliminary report, by K. Kolev (Environmental Research, 1982).

The study

• Author: K. Kolev
• Journal: Environmental Research
• Published: 1982;29(1):123-33
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The experiment was performed on white rats that were administered intraperitoneally two types of crocidolite asbestos-fibrous and amorphous. The fibrous structure, with fiber length ranging between 3 and 5 µm, and the amorphous state of the second type were proved by electron microscopy and infrared spectrophotometry. In the group treated with amorphous asbestos, at an average interval of 484 days after the administration, eight cases of mesothelioma were observed, while in the group treated with fibrous asbestos only three cases of mesothelioma were found, i.e., the results obtained show a statistically significant difference. The fibrous structure of asbestos as the predominant cause of peritoneal mesothelioma induction is questioned and a new explanation of the fact that amorphous asbestos induces approximately three times as many cases of mesothelioma than fibrous asbestos is considered.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This was a rat experiment, published as a preliminary report. The author divided female Wistar rats into three groups of 20. Group 1 received an intraperitoneal (abdominal cavity) injection of UICC crocidolite ground for 2 hours until no fibrous structure remained, which the author called amorphous asbestos. Group 2 received crocidolite fibers, 90% of them 3 to 5 micrometres long. Group 3 received only salt solution. Each treated rat was given 50 mg of dust in 1 ml of saline. Mesothelioma was confirmed under the microscope in eight rats in group 1 (about 40%) and three rats in group 2 (about 15%). No tumors were seen in the control group. The author reported the difference between the asbestos groups as statistically significant. According to the text, group 1 tumors appeared from day 281 to day 547, but Table 1 lists one at day 549. Group 2 tumors appeared from day 375 to day 527. Tumor structure did not differ significantly between the groups. The author questioned whether the fibrous shape of asbestos is the main cause of peritoneal mesothelioma. Tissue from rats without visible tumors was still being examined.

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 (preliminary report) comparing intraperitoneal injection of amorphous versus fibrous crocidolite asbestos with a saline control group
• Who was studied: Female Wistar rats (100 to 110 g initial body weight), 60 in total, in three groups of 20. Injections were given on 9 March 1978, and the experiment ended on day 862.
• Exposure: UICC crocidolite asbestos in two forms. Group 1 received amorphous asbestos (ground 2 hours in an agate ball mill, about 99% isometric particles, no fibers seen by electron microscopy). Group 2 received fibrous asbestos (ground 30 minutes and water-separated, 90% of fibers 3 to 5 micrometres long). Group 3 received saline only. Each animal received a single intraperitoneal injection of 50 mg dust in 1 ml of saline.
• Main results:
  • Group 1 (amorphous crocidolite): 8 of 20 rats had histologically confirmed mesothelioma (about 40%).
  • Group 2 (fibrous crocidolite): 3 of 20 rats had mesothelioma (about 15%). Group 3 (saline control): no neoplasms.
  • The author reported the difference in mesothelioma numbers between group 1 and group 2 as significant, using an F criterion with p = 0.05 (1.89 greater than 1.69).
  • Timing in group 1: the discussion says mesotheliomas appeared between day 281 and day 547 after injection, but Table 1 lists a group 1 case at day 549 (arithmetic mean 484 days). Timing in group 2: tumors appeared between day 375 and day 527 (arithmetic mean 466 days).
  • Hemorrhagic ascitic fluid was found in four group 1 animals. In two of these, it contained many giant multinuclear tumor cells of mesothelial origin.
  • Tumor histological structure did not differ significantly between the two asbestos groups.
  • Group 2 (fibrous) tumors had more fibrous tissue around the cancer cells, and asbestos fibers were seen. In group 1 (amorphous), fibrosis was scarcer, and asbestos and giant cell forms were not observed.
• The authors' conclusion: The author concluded that the view that fibrous structure is the main factor causing peritoneal mesothelioma can be questioned. The author proposed that other factors, such as surface activity, crystal lattice breakdown and liberated metals, play a decisive role, and that the needle-like shape of asbestos may be only a cocarcinogenic (contributing) factor. The author also stated that permissible asbestos limits should take into account submicroscopic fractions and amorphous particles, not only fibers over 8 micrometres long.
• Limitations the authors state:
  • This is a preliminary report. Histological examination of tissue from animals without visible tumors, whether they survived to day 862 or died naturally, was still in progress.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Crocidolite, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Crocidolite, Fiber Length, Peritoneal Mesothelioma.

Related studies

• Differential diagnosis of malignant tumours in the abdominal cavity of rats after intraperitoneal injection of crocidolite or benzo[a]pyrene — J. Friemann, M. Varnai, et al. (1996)
• Characteristics of tumors and tumor cells cultured from experimental asbestos-induced mesotheliomas in rats — J.E. Craighead, N.J. Akley, et al. (1987)
• Pathogenesis of experimentally induced asbestos mesothelioma in rats — L.A. Vasilieva, L.N. Pylev, et al. (1998)
• P53 mutations in tumours induced by intraperitoneal injection of crocidolite asbestos and benzo[a]pyrene in rats — K. Unfried, N. Kociok, et al. (1997)
• Pulmonary bombesin in experimentally induced asbestosis in rats — R. Day, I. Lemaire, et al. (1985)
• Absence of carcinogenic response to multiwall carbon nanotubes in a 2-year bioassay in the peritoneal cavity of the rat — J. Muller, M. Delos, et al. (2009)

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