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EC number: 204-066-3
CAS number: 115-11-7
incidences of non-neoplastic nasal lesions are shown below. Hyaline
degeneration of the olfactory epithelium is considered a nonspecific
adaptive response to prolonged inhalation of irritant material and has
no adverse effect on affected animals (OECD SIDS Report for Isobutylene,
2003). The increased goblet cell hypertrophy in the was however
considered to be adverse.
Incidences of Non-neoplastic Lesions of the Nose
Number Examined Microscopically
Olfactory Epithelium, Degeneration Hyaline (a)
Goblet Cell Hypertrophy
a Number of animals with lesion
b Average severity grade of lesions in affected animals: 1=minimal, 2=mild, 3=moderate, 4=marked
50 male and 50 female F344/N rats were exposed to isobutene (greater
than 98% pure) at concentrations of 0, 500, 2000, or 8000 ppm (1147,
4589, 18359 mg/m3)
6 hours per day, 5 days per week, for 105 weeks. Survival of exposed
males and females was similar to that of the chamber controls. Mean body
weights of exposed groups were generally similar to those of the chamber
controls throughout the study.
acid (HIBA) the major urinary metabolite of isobutene, was measured in
the urine of the rats as an indicator of isobutene exposure. The amount
excreted increased with increasing exposure concentration but when HIBA
concentration was normalized to isobutene exposure concentration, the
relative amount of HIBA excreted decreased with increasing exposure
concentration, implying nonlinear kinetics.
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