Lipid peroxides in middle ear fluid after acute otitis media in guinea pigs

Oxygen free radical damage has been demonstrated in the middle ear mucosa o f a. guinea pig model of acute otitis media (AOM). Potential sources of fre e radicals include both neutrophils responding to infection and Streptococc us pneumoniae, a common AOM pathogen. This project was conducted to examine the middle ear fluid in a guinea. pig model of AOM for evidence of elevate d lipid peroxide (LPO) as a marker of free radical damage. Twenty-one guine a pigs were injected transtympanically with bacteria into the left (infecte d) middle ear cavity and sterile saline into the right (control) middle ear . Middle car fluid was recovered on postoperative day 5. The fluid was weig hed and analyzed for quantity of LPO. Results indicated an increased absolu te level of LPO, as well as an increased level of LPO divided by the weight of the fluid recovered. Histologic examination confirmed leukocyte infiltr ation and mucosal edema that were consistent with mucosal damage. While fre e radical damage to the middle ear mucosa in a guinea pig model of AOM is w ell documented, this is the first study to demonstrate evidence of foe radi cal damage in middle ear fluid. These results are relevant because they cor relate mucosal damage with lipoperoxidation in fluid. Additionally! this se rves as an important precursor to human studies, since middle ear fluid is readily available in patients with otitis media.