Orotracheal instillation of gastric juice: Species variations in acute lung injury relate to differences in matrix metalloproteinase activity

Gastric content aspiration is common in the elderly and people with neurological conditions. It is unknown if early events predict final outcomes after aspiration. To gain further knowledge we studied rat and hamster species variations in acute lung injury (ALI) by a single orotracheal dose of gastric juice (GJ). Under Ketamine/Xylazine, Sprague-Dawley rats and Syrian Golden hamsters received 1.5ml/Kg body wt. of GJ from a pool for each species (similar pH, pepsin activity and particle type). ALI markers (lung wet/dry weight ratio, histological changes, and BALF protein content) and lung matrix metalloproteinase-9 (MMP-9) activity were measured 4, 12, 24h, and 4 days(d) later (n=10/time point/species). Statistical analysis: ANOVA. In rats, lung wet/dry weight ratio increased at 4h (p Conclusion: ALI by a single dose of GJ is more severe in hamsters than in rats and is associated with a long-lasting increase in MMP-9 activity. Early species variations in MMP-9 activity could be associated with species differences in chronic damage if aspiration events become repetitive. Funding: FONDECYT 1120943.