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EC number: 204-340-2
CAS number: 119-64-2
Result: not teratogenic
MATERNAL TOXIC EFFECTS BY DOSE LEVEL:
- Mortality: There was no treatment-related death.
- Description, severity, time of onset and duration of clinical signs: Clinical signs did not occur.
- Body weight: Slightly decreased in high dose group, statistically significant (p<=0.05) on days 9 (-3%), 18 (-5%), and 20 (-5%).
A significantly lower body weight gain was recorded for the whole treatment period (0-20: -15%).
Body weights slightly
decreased also in the mid dose group with statistical significance on days 9 (-11%) and 13 (-6%) and subsequent adaptation to
normal, thus considered to be of questionable biological relevance. Normal in low dose group.
- Food/water consumption: Food consumption distinctly to slightly decreased in high dose group, statistically significant on study days
6-9: -33%; 9-13: -12%; 13-16: -10%; 16-18: -12% (absolute);
6-9: -32%; 9-13: -10%; 13-16: -7%; 16-18: -9% (relative).
Food consumption slightly to marginally lower in mid dose females, attaining statistical significance on days 6-9 (-15% abs.,
-16% rel.) and 13-16 (-6% abs. and rel.) only. Normal in low dose group.
- Number pregnant per dose level: 22/24; 22/24; 23/24; 23/24 (control / low / mid / high dose) = not affected. One control female
was pregnant with only corpora lutea and empty implantation sites
- Number aborting: no abortions
- Number of resorptions: no total resorptions
- Number of implantations: 13.6; 14.5; 13.6; 13.7 (control / low / mid / high dose) = not affected.
- Pre and post implantation loss: 4.9; 6.2; 8.3; 10.9% pre-implantation loss (%corpora lutea) (means of control / low / mid / high dose). One total post implantation loss in control group.
- Number of corpora lutea: 14.3; 15.5; 14.6; 15.4 (means of control / low / mid / high dose).
- Gross pathology incidence and severity: No compound-related gross lesions were observed at necropsy.
- Organ weight changes: Insignificantly lower uterus weight for high dose females (-7%).
There were no findings at caesarian section in any group of fetuses which could be related to the test substance administration.
There was no statistically significant difference in the mean crown-rump length for either male or female fetuses in any group.
However, evaluation of both genders together revealed a slight but statistically significant (p<=0.05) decrease of the mean
crown-rump length for all high dose fetuses against the control (-2.3%).
The mean placenta weight was slightly but statistically significantly (p<=0.05) decreased in the high dose group
(0.52; 0.51; 0.51; 0.46 g in control, low, mid, and high dose groups, respectively).
Though considered not biologically significant, a treatment-related influence on these endpoints could not be excluded.
- Litter size and weights: mean weights 3.64; 3.61; 3.64; 3.56 g = not affected
- Number viable: Total number of live fetuses 12.4; 13.7; 13.0; 12.6 (control / low / mid / high dose) = not affected. No dead fetuses.
- Sex ratio: 44.4; 46.3; 44.6; 52.4% males (control / low / mid / high dose) = not affected
- Grossly visible abnormalities: no substance-related findings
- External abnormalities: no substance-related findings
- Soft tissue abnormalities: no substance-related findings
- Skeletal abnormalities: Isolated findings of statistical significance for high-dosed fetuses at the thoracic vertebra centra and in the
rib (here also for low-dosed fetuses): There was 1 fetus (out of 152, i.e. 0.7%) in the high dose group with a tail aplasia and
spina bifida occulta as a major defect, associated with several skeletal minor defects on the vertebra and skeletal retardations.
This complex finding was associated secondary to insufficient oxygen supply of this fetus, which is known to occur incidentally
during embryonal development within relatively large litters (14 fetuses in total in this litter). In the absence of correlating findings
either in other fetuses or other litters of this group, these findings were considered to be incidental.
Minor skeletal defects of statistical significance included aplasia/fused/fragmented thoracic vertrebra centra in 0% (control),
0.6% (low dose), 0% (mid dose), and 2.0% (high dose, p<=0.05) animals. As the incidences were only slightly above inhouse
control data (0-1.5%) and did not follow a dose response relationship, they were considered to be incidental. Another minor defect
of statistical significance was uni- or bilateral knoddy ribs in 0% (control), 3.2% (low dose, p<=0.05), 0% (mid dose), and 7.9%
(high dose, p<=0.05) animals. As historical control data were not yet available for this endpoint and the occurrence of this effect
did not follow a dose response relationship, it was considered to be incidental.
Daily oral (gavage) administration of Tetrahydronaphthalene at a dose
level of 135 mg/kg bw/day during the sensitive phase of organogenesis
and intrauterine development (days 6 – 20) of the fetuses induced
decreased body weight gains and food intake during the treatment phase,
which were interpreted as a first sign of maternal toxicity, without
significantly altering pregnancy of the dams and intrauterine
development of the conceptuses.
There was no maternal or embryofetal/developmental toxicity observed
after administration of Tetrahydronaphthalene at either 45 or 15 mg/kg
body weight/day. Tetrahydronaphthalene was not teratogenic in the rat.
The 'No Observed Adverse Effect Level' (NOAEL) was 45 and > 135 mg/ kg
body weight/day for maternal and developmental effects, respectively.
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