Acute inhalation studies with @entity36419 vapor. I. Methodology and LC50 determinations in XXXX , @entity35 , and @entity19 .

@entity308 @entity2332 @entity3126 @entity29154 @entity19 @entity384 @entity840 @entity1576 @entity35 @entity36419 @entity204 @entity2055
Groups of male and female Fischer 344 @entity35 , B6C3F1 @entity19 , and Hartley @entity840 were exposed once for 6 hr to mean concentrations of 10.5, 5.4, 2.4, 1.0, or 0 (control) ppm of @entity36419 ( @entity29154 ) vapor. @entity35 and @entity19 were also exposed to 20.4 ppm of MIC. No @entity204 occurred in animals exposed to 2.4 or 1.0 ppm. The majority of @entity204 for the 20.4- and 10.5-ppm groups occurred during postexposure Days 1 through 3, while at 5.4 ppm @entity204 were observed throughout the 14-day postexposure period. The 6-hr LC50 values (with 95% confidence limits) were 6.1 (4.6 to 8.2) ppm for @entity35 , 12.2 (8.4 to 17.5) ppm for @entity19 , and 5.4 (4.4 to 6.7) ppm for @entity840 . Notable clinical observations during and immediately following MIC exposure were lacrimation, perinasal/perioral wetness, @entity1576 (e.g., mouth breathing), decreased activity, @entity2055 , and @entity2332 . The frequency of clinical signs decreased during the second postexposure week. Body weight losses were common in all species following MIC exposures of 2.4 ppm or greater. At 1.0 ppm, only female @entity19 had body weight @entity308 . Recovery of body weight loss was observed in the 5.4- ( @entity840 only), 2.4- and 1.0-ppm concentration groups. The lungs of all animals that died were discolored. Following microscopic examination of the respiratory tract, @entity204 were attributed to @entity3126 and @entity384 . In a separate study, Fischer 344 @entity35 and Hartley @entity840 were exposed once for 4 hr to mean concentrations of 36.1, 25.6, 15.2, or 5.2 ppm of MIC vapor. In general, the results were similar to those of the single 6-hr exposure study.
