Effects of Repeated Exposures to Ozone and Nitrogen Dioxide on Respiratory Tract Prostanoids

Abstract

Prostanoids (prostaglandins, thromboxanes) are mediators of various physiological functions in the respiratory tract. The toxic action of air pollutants may include the ability to alter prostanoid metabolism. Rabbits were exposed to 0.3 ppm O₃ 3 ppm NO₂, or their combination, for 2 h/day for up to 74 days. Levels of selected prostanoids in bronchopulmonary lavage fluid were assessed after 7 (t₇) and 14 (t₁₄) exposures, and again at 24 h following the last exposure (t₁₅) Ozone resulted in a significant decrease in prostaglandin E₂ at t₁₄ and t₁₅, while NO₂ and the pollutant mixture resulted in a decrease in prostaglandin E₂ at all three of the time points examined. Levels of 6-keto-prostaglandin-F_1a were depressed at t₁₅ following exposure to either NO₂ or to the mixture. No effects on thromboxane B₂ or prostaglandin F_2a were found. The responses to the mixture did not suggest any synergism but, depending upon the specific prostanoid, were either additive or similar to that due to either O₃ or NO₂ when inhaled singly.