EICOSANOID SYNTHESIS AND INACTIVATION IN HEALTHY AND INFECTED CHINCHILLA MIDDLE EARS

Otitis media (OM) is an inflammatory reaction of the middle ear (ME) e licited by a variety of stimuli including tubal obstruction, allergy a nd bacterial infection. The leukotrienes and prostaglandins are among the earliest mediators produced in response to these insults. Their me asured levels in human and animal models span a broad range of concent rations. However, their baseline levels and metabolic fates are unknow n for the ME. Their dynamics in the ME were examined using the chinchi lla animal model, tritiated eicosanoids and a lavage procedure. Prosta glandin levels in the normal ME were 10 times higher than the 34 pg/ea r observed for the leukotrienes and thromboxane B-2. These levels were significantly increased by the calcium ionophore A23187 and bacterial infection. Leukotrience C-4 was the most and prostaglandin E-2 the le ast persistent eicosanoid in the ME. Their residence time in the ME wa s increased by infection. The rank order of eicosanoid concentrations among comparable studies was surprisingly constant, with prostaglandin E-2 the most abundant and the leukotrienes the least. Comparisons of eicosanoid levels from A23187 stimulation and the infectious models sa mpled at 3 days suggest that the higher levels observed in the infecti ous models may represent basal eicosanoid production for hyperplastic ME mucosa.