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EC number: 217-496-1
CAS number: 1873-88-7
In an oral repeated dose toxicity study
(combined with a reproduction/developmental toxicity screening test),
performed to GLP and conducted according to OECD Guideline 422,
1,1,1,3,5,5,5-heptamethyltrisiloxane was assessed for its toxicity in
Four groups of ten male and ten female rats
were treated by oral gavage with the test material (in corn oil) at 0,
50, 200 or 800 mg/kg bw/day. Following two weeks of treatment, animals
were allowed to mate for up to two weeks. In total, males were treated
for at least 28 days (including the pre-mating period of 14 days), while
females were treated for approximately 49 days (a pre-mating period of
14 days, a mating period of up to 14 days, throughout gestation and up
until 4 days post-partum). Animals were observed throughout the study
for any overt signs of toxicity or morbidity, until sacrifice and gross
necropsy. Changes in body weight, food consumption, and clinical
chemistry and haematology were recorded.
All animals survived until scheduled
necropsy and there were no clinical signs of toxicity (signs of
discomfort such as increased salivation were noted but were not
considered to be toxic effects).
Males given 800 mg/kg bw/day demonstrated
significantly reduced food consumption during the second week of the
study. Significant decreases in body weight and body weight gain were
noted in males given at least 200 mg/kg bw/day. Levels of cholesterol
were significantly increased, and total bilirubin significantly
decreased in males given 800 mg/kg bw/day. In females given at least 200
mg/kg bw/day, the absolute and relative weight of the liver was
significantly increased in a dose-dependent manner, while males given
800 mg/kg bw/day also demonstrated significant increases in liver, and
kidney, weight. Adverse, apparently substance-related microscopic
findings were reported in the kidneys and livers of males given at least
200 mg/kg bw/day and 800 mg/kg bw/day respectively, and included protein
droplet nephropathy, kidney tubular degeneration/regeneration, and
hepatic brown pigment accumulation. A number of microscopic “adaptive
changes” were also seen in the spleen and thyroid gland of females given
at least 200 mg/kg bw/day and in males given 800 mg/kg bw/day.
From these results, a
no-observed-adverse-effect level (NOAEL) of 200 mg/kg bw/day was
assigned to males and females for general toxicity, based on the
microscopic findings in the liver (hepatic brown pigment accumulation)
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