Abstract
Background: Microcystin-LR (MCYST-LR) is a toxin commonly released by cyanobacteria in water reservoirs. It can damage the lung if absorbed by oral, venous or respiratory routes.
Aim: To verify the putative lung mechanical and histological impairment and the upper airways of mice after chronic intra-nasal instillation of MCYST-LR.
Methods: Male Swiss mice (25-30 g) were daily intranasally instilled with 10 μL of distilled water (AD group, n=10) or 6.7 ng/kg of MCYST-LR diluted in 10 μL of distilled water (TOX, n=8) 7 days/week for 1 month. Lung mechanics was determined 24 h after the last instillation. Lungs and nasal cavity were prepared for histological analysis (hematoxylin-eosin and alcian blue, respectively).
Results: TOX showed higher static elastance and viscoelastic component of elastance (33.9±1.2 and 5.2±0.4 cmH2O/mL, respectively), viscoelastic/inhomogenous pressure and total resistive pressure (1.0±0.1 and 2.0±0.2 cmH2O, respectively) than AD (26.4±2.6 and 3.7±0.3 cmH2O/mL, 0.7±0.1 and 1.5±0.1 cmH2O, respectively). Alveolar collapse and polymorphonuclear cell content were significantly larger in TOX group (41.2%, and 8.1×10-3 cells/mm2) than in AD (3.1% and 2.3×10-3 cells/mm2). TOX displayed a significantly higher volume proportion of mucous substances in the nasal epithelium (61.5%) than AD (38.5%). T-test was used (α = 5%).
Conclusion: Prolonged exposure to low levels of microcystin-LR triggered pulmonary tissue mechanical impairment, damage to lung histology and secretory changes in the nasal cavity of mice. Thus, frequent exposure to low levels of MCYST-LR can damage the respiratory system and should be avoided.
Supported by: CNPq, FAPERJ, MCT
- © 2011 ERS
