Several physiological effects of ozone exposure involving smooth muscle contracting substances have been studied in Sprague-Dawley derived, male rats whose body weights were in the range of 180-250 grams and whose ages were in the range of 45-60 days. The ozone concentration of interest was 0.5-1.O ppm and the exposure time was four hours. However, higher concentrations of ozone and longer exposure times were sometimes employed. It was observed that the exposure of these rats to ozone concentrations of 0.5 or 1.0 ppm for 4.0 hours produced the following effects in their lungs: (a) caused the release of prostaglandin F2 alpha (PGF2 alpha) and thromboxane A2 (TXA2), (b) increased the angiotensin converting enzyme activity, and (c) decreased the uptake of serotonin from the blood. Histamine and slow reacting substance of anaphylaxis (SRS-A) were not released nor was the histamine forming capacity of the lung altered. Edema formation was observed in the rats from one supplier, but not in those from another and succinoxidase activity was observed to be decreased by short exposure to ozone and increased by long exposure, as reported by previous investigators.

Caption title. "July 1981." "EPA-600/1-81-051." Microfiche.