title: Biopersistence of potassium hexatitanate in inhalation and intratracheal instillation studies.
abstract: An inhalation study and an intratracheal instillation study were conducted to evaluate the biological effects of the new chemical, potassium hexatitanate (PH). For the inhalation study, Wistar male rats were exposed to PH for 6 h a day, 5 days a week for a period of 3 months. The mass median aerodynamic diameter of PH in the exposure chamber was 4.9 µm (1.8) and the mean concentration during the exposure was 2.3 ± 0.1 mg/m(3). After the 3-month inhalation period, rats were dissected at 3 days, 1 month, 3 months, 6 months, and 12 months. The initial PH burden was 0.17 ± 0.03 mg/lung, and this decreased exponentially up to 6 months after inhalation. After 6 months, the rate at which the burden decreased slowed. The biological halftime up to 6 months after exposure was 2.3 months. No difference was found in the dimension of PH fibers in the lung during the observation period and the histopathological examination found no remarkable inflammation or fibrosis. For the intratracheal instillation study, the rats were given a single 2-mg dose of PH suspended in a 0.4 ml saline solution. The geometric mean diameter was 4.3 µm (2.3). After instillation, the rats were dissected at 3 days to 12 months. The PH burden in the lungs decreased exponentially and the biological halftime was 3.1 months. The results of the dimension of PH and histopathological findings were the same as those for the inhalation study. These data suggest that the toxicity of PH in the lung is low in these doses.
authors.affiliation: Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Kitakyushu, Fukuoka, Japan. mk2snipe@med.uoeh-u.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Takako
authors.initials: T
authors.lastname: Oyabu
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Morimoto
authors.forename: Akira
authors.initials: A
authors.lastname: Ogami
authors.forename: Chikara
authors.initials: C
authors.lastname: Kadoya
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Nishi
authors.forename: Motoi
authors.initials: M
authors.lastname: Todoroki
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Myojo
authors.forename: Isamu
authors.initials: I
authors.lastname: Tanaka
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D006863:Hydrogen-Ion Concentration; D019570:Inhalation Exposure; D008168:Lung / Q000187:drug effects / Q000473:pathology*; D008297:Male; D010316:Particle Size; D017680:Potassium Compounds / Q000493:pharmacokinetics*; D051381:Rats; D017208:Rats, Wistar; D014025:Titanium / Q000493:pharmacokinetics*; D014132:Trachea / Q000378:metabolism*
chemical_list: D017680:Potassium Compounds; D014025:Titanium