Pathological features of rat lung following inhalation and intratracheal instillation of C₆₀ fullerene

Abstract

We evaluated the pulmonary pathological features of rats that received a single intratracheal instillation and a 4-week inhalation of a fullerene. We used fullerene C₆₀ (nanom purple; Frontier Carbon Co. Ltd, Japan) in this study. Male Wistar rats received intratracheal dose of 0.1, 0.2, or 1 mg of C₆₀, and were sacrificed at 3 days, 1 week, 1 month, 3 months, 6 months, and 12 months. In the inhalation study, Wistar rats received C₆₀ or nickel oxide by whole-body inhalation for 6 h/day, 5 days/week, 4 weeks, and were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. During the observation period, no tumors or granulomas were observed in either study. Histopathological evaluation by the point counting method (PCM) showed that a high dose of C₆₀ (1 mg) instillation led to a significant increase of areas of inflammation in the early phase (until 1 week). In the inhalation study of the C₆₀-exposed group, PCM evaluation showed significant changes in the C₆₀-exposed group only at 3 days after exposure; after 1 month, no significant changes were observed. The present study demonstrated that the pulmonary inflammation pattern after exposure to well-characterized C₆₀ via both intratracheal and inhalation instillation was slight and transient. These results support our previous studies that showed C₆₀ has no significant adverse effects in intratracheal and inhalation instillation studies.

Keywords::

• Fullerene
• inhalation
• instillation
• rat
• pulmonary toxicity