OZONE TOXICITY IN THE MOUSE - COMPARISON AND MODELING OF RESPONSES INSUSCEPTIBLE AND RESISTANT STRAINS

Previous studies from this laboratory have demonstrated a concentratio n-related hypothermia and increases in bronchoalveolar lavage (BAL) fl uid indexes of toxicity in the rat after exposure to environmentally r elevant levels of ozone (O-3) In similar studies with C5liBL/6J (B6) a nd C3H/HeJ (C3) mice, other investigators have reported differential e ffects on BAL toxicity indexes between the two strains after O-3 expos ure. The present study investigated the relationship between the repor ted strain differences in BAL parameters in B6 and C3 mice exposed to O-3 and the induced hypothermic response. Male 80-day-old mice (n = 94 , 47/strain) were used for these studies. Subsets (n = 8/strain) of th ese animals were surgically implanted with radiotelemetry transmitters that permitted continuous monitoring of core body temperature and act ivity. All telemetry animals and an equal number of nontelemetry anima ls (n = 8/strain) were exposed to filtered air for 24 h followed by a 2-h exposure to 2 parts/million O-16(3). With use of a similar protoco l, groups of nontelemetry mice (n = 12/strain) were exposed to either filtered air or 2 parts/million O-18(3) for 2 h. At 0 or 22 h postexpo sure, mice were anesthetized with halothane and intubated, and their l ungs were lavaged with 37 degrees C saline. Although both strains of m ice exhibited significant abrupt decreases in core body temperature on exposure to O-3 and both recovered rapidly after cessation of the O-3 exposure, the response of the C3 mice was more dynamic than that of t he B6 mice. Similarly, both strains showed characteristic changes in b iomarkers of O-3 toxicity; however, the increases in BAL fluid protein and cells at 22 h postexposure were significantly greater and the per centage of neutrophils was significantly less in B6 mice than in C3 mi ce. It is possible that the strain differences in BAL constituents may be related to the differences in the hypothermic response.