title: Effect of particle size of intratracheally instilled crystalline silica on pulmonary inflammation.
abstract: Crystalline silica, known as a causal substance of silicosis, has been carefully evaluated for its carcinogenicity and fibrogenicity. In this study, we instilled crystalline silica of two different size (S(1.8) :1.80 microm (S.D. 2.0), S(0.7) :0.74 microm (S.D. 1.5)) into the trachea of rats to evaluate the size effects of the particles on pulmonary inflammation. S(1.8) and S(0.7) samples were administered to rats by a single intratracheal instillation (2 mg/ 0.4 ml saline). At three days, 1 wk and 1, 3 and 6 months after the instillation, the blood, bronchoalveolar lavage fluid (BALF), and pulmonary tissues were analyzed. Six images per HE-stained section were digitally captured and examined by the point counting method (PCM). Polymorphonuclear leukocyte (PMN)-in-blood specimens and cytospin specimens from BALF were stained immunohistochemically with BrdU. At six months after the instillation, the effects on inflammatory cells in the pulmonary tissues and BALF tended to be more marked in the rats instilled with S(1.8) than those instilled with S(0.7). Particularly, clear differences were observed in the number of inflammatory cells in BALF. Even if the particles are of the same chemical composition, the results suggest that, their biological effects vary depending on their particle size. Therefore, when such particles are used in workplaces, strict control systems should be established according to the risks present by different sizes of particles.
authors.affiliation: Department of Environmental Health Engineering, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Iseigaoka, Fukuoka, Japan.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Kajiwara
authors.forename: Akira
authors.initials: A
authors.lastname: Ogami
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamato
authors.forename: Takako
authors.initials: T
authors.lastname: Oyabu
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Morimoto
authors.forename: Isamu
authors.initials: I
authors.lastname: Tanaka
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001772:Blood Cell Count; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D008297:Male; D010316:Particle Size; D011014:Pneumonia / Q000209:etiology*; D051381:Rats; D017208:Rats, Wistar; D012822:Silicon Dioxide / Q000008:administration & dosage / Q000633:toxicity*; D014132:Trachea
chemical_list: D012822:Silicon Dioxide