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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
From 9 JAN 2002 to 21 FEB 2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study (EU B7 and OECD 407)
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
[Please provide information for all of the points below. Indicate if further information is included as attachment to the same record, or elsewhere in the dataset (insert links in 'Cross-reference' table)]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
[Describe why the read-across can be performed (e.g. common functional group(s), common precursor(s)/breakdown product(s) or common mechanism(s) of action]

It is hypothesized that the target chemical and the following chemical as source chemicals should exhibit comparable toxicity profiles:

• 3,5,5-trimethylhexanoic acid

It is proposed to use the toxicity data of the mentioned source chemicals to fulfill the data requirement for the target chemical on the human health endpoint 'repeated dose toxicity'. 3,5,5-trimethylhexanoic acid is a presumed metabolite.

The underlying scientific rationale for the use of 3,5,5-trimethylhexanoic acid as source chemical is based on the metabolism consideration. Upon absorption, the target chemical is expected to undergo a degradation process, resulting in the systemic release of 3,5,5-trimethylhexanoic acid, thereby providing the justification for the read-across especially for the mid- and long term toxicities such as repeated dose toxicity and reproduction toxicity.

The proposed approach applies for all exposure routes (oral/dermal/inhalation), because both the target chemical and source chemicals are expected to be bioavailable by all exposure routes and the systemic release of the presumed metabolite is less dependent on exposure route.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
[Provide here, if relevant, additional information to that included in the Test material section of the source and target records]

Target chemical:
6-(isononanoylamino)hexanoic acid, compound with 2,2`,2``-nitrilotriethanol; CAS: 85702-79-0

Source chemicals:

3,5,5´-trimethylhexanoic acid; CAS: 3302-10-1

The target chemical is a mono-substituent substance, the analytical purity being >99%. The source chemical is the raw materials (3,5,5´-trimethylhexanoic acid ) of the target chemical. A toxicity difference due to different impurity profiles is not likely to occur.

3. ANALOGUE APPROACH JUSTIFICATION
[Summarise here based on available experimental data how these results verify that the read-across is justified]

Justification for the use of 3,5,5-trimethylhexanoic acid as source chemical:

- 3,5,5-trimethylhexanoic acid is the presumed metabolite of 6-(isononanoylamino)hexanoic acid. It is also the presumed metabolite of 6-(isononanoylamino)hexanoic acid, compound with 2,2`,2``-nitrilotriethanol.
This view is based on the results of the metabolites investigation in degradation samples obtained in a Zahn-Wellens test. The β-oxidation at the terminal carboxylic acid moiety in combination with hydrolysis at amide bond could be assumed as the degradation pathway leading to 3,5,5-trimethylhexanoic acid as a stable metabolite.
Also the hydrolysis at the amide moiety is thinkable. The hydrolysis products would be then 3,5,5-trimethylhexanoic acid and 6-aminocaproic acid. The latter compound is a drug known as amicar and is expected to be far more rapidly eliminated than 3,5,5-trimethylhexanoic acid. A significant toxicity attribution of 6-aminocaproic acid cannot be derived.
One literature article was found, describing further biotransformation of 3,5,5-trimethylhexanoic acid in rat: gamma-lactone of 3,5,5-trimethylhexanoic acid is formed, which may be the ultimate toxicant for the alpha-2u-globulin accumulation in kidneys.
As mentioned above no significant toxicity contribution of 2,2`,2``-nitrilotriethanol is expected.

-The findings in the 28-day oral toxicity study on the 3,5,5-trimethylhexanoic acid are comparable to those found in the repeated dose toxicity studies of the target chemical and 6-(isononanoylamino)hexanoic acid:
- liver and kidney enlargement
- peroxisome proliferation in the liver
- The alpha-2u-globulin accumulation in kidneys.

4. DATA MATRIX

Data matrix and other information see the attached read-across justification in chapter 13

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2002
Report Date:
2002

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
EU Method B.7 (Repeated Dose (28 Days) Toxicity (Oral))
Qualifier:
according to
Guideline:
OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity in Rodents)
GLP compliance:
yes (incl. certificate)
Remarks:
according to German Chemikaliengesetz, §19
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles river, Sulzfeld, Germany
- Age at study initiation: 36 +/- 1 days
- Housing: individual
- Diet: Kliba maintenance diet, Provimi Kliba, Kaiseraugst, Switzerland, ad libitum
- Water: ad libitum
- Acclimation period: about 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 30-70
- Air changes (per hr): not stated
- Photoperiod (hrs dark / hrs light): 12 h/12 h

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: 0.1% aqueous solution of Cremophor EL
Details on oral exposure:
The test substance preparations were administered to the animals at a volume of 10 mL/kg body weight, based upon the latest individual body weight determination.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The stability of the test substance in an aqueous solution of 0.1% Cremophor EL in aqua bidest over a period of 7 days at room temperature was tested prior to the start of the study. Homogeneity analyses of the test substance preparations were carried out in samples of the highest and lowest concentration drawn from the bottom, middle and the top of the emulsion at the start of the administration period. These samples also served for concentration control analyses. Additional concentration control analyses were performed with samples from the mid concentration drawn from the middle of the emulsion at the start of the administration period. The analyses were carried out as a separate study at the test facility GKA Analytik of BASF Aktiengesellschaft under the responsibility of the Study Director of this test facility. The study was carried out in compliance with the Principles of Good Laboratory Practice.
Duration of treatment / exposure:
28 days (4 weeks)
Frequency of treatment:
daily by gavage
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 10, 50, 200 mg/kg bw/d
Basis:
actual ingested
No. of animals per sex per dose:
10 animals per sex in controls and high dose group (group 3), each 5 of them examined at the end of exposure (main group), the remaining after a recovery period of 14 days (recovery group),
5 in low and mid dose groups (groups 1 and 2) of main study, no recovery groups
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: based on a 2 weeks pilot study with dose levels of 100, 300 and 1000 mg/kg bw/d (liver and kidney effects at all dose levels)
- Post-exposure recovery period in satellite groups (only controls and high dose): 14 days

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: The animals were examined for evident signs of toxicity or mortality twice a day (in the morning and in the late afternoon) from Mondays to Fridays and once a day (in the morning) an Saturdays, Sundays and public holidays.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Further clinical examinations were carried out daily just before treatment and less than 1 hour after treatment, as well as between 3 and 4 hours after treatment, as well as once a day during the recovery period.
The following parameters were examined: abnormal behavior during "handling", fur, skin, posture, salivation, respiration, activity/arousal level, tremors, convulsions, abnormal movements, impairment of gait, lacrimation, palpebral closure, exophthalmus, feces (appearance/consistency), urine, pupil size


BODY WEIGHT: Yes
- Time schedule for examinations: Body weight was determined before the start of the administration period in order to randomize the animals. During the administration period and the recovery period the body weight was determined on day 0 (start of the administration period) and thereafter at weekly intervals. The difference between the body weight on the respective day of weighing and the body weight on day 0 was calculated as body weight change.


FOOD EFFICIENCY:
Food consumption was determined weekly over a period of 7 days and calculated as mean food consumption in grams per animal and day.


OPHTHALMOSCOPIC EXAMINATION: Yes
see above ( "clinical observations")


HAEMATOLOGY: Yes
- Time schedule for collection of blood: Blood was taken from the retroorbital venous plexus in the morning from fasted animals without anesthesia. The blood sampling procedure and the subsequent analysis of the blood and serum samples were carried out in a randomized sequence.
- Parameters checked: leukocytes, erythrocytes, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, platelets, differential blood count, differential blood smears, prothrombin time


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Blood was taken from the retroorbital venous plexus in the morning from fasted animals without anesthesia. The blood sampling procedure and the subsequent analysis of the blood and serum samples were carried out in a randomized sequence.
- Parameters checked: alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, serum-y-glutamyltransferase, cyanide-insensitive Palmitoyl-CoA-oxidation, sodium, potassium, chloride, inorganic phosphate, calcium, urea, creatinine, glucose, total bilirubin, total protein, albumin, globulins, triglycerides, cholesterol, magnesium


URINALYSIS: Yes
- Time schedule for collection of urine: For urinalysis the individual animals were transferred to metabolism cages (withdrawal of food and water) and urine was collected overnight. The urine samples were evaluated in a randomized sequence.
- Parameters checked: volume, colour, turbidity, pH, protein, glucose, ketones, urobilinogen, bilirubin, blood, specific gravity, sediment


NEUROBEHAVIOURAL EXAMINATION: Yes
A functional observational battery was performed in all animals at the end of the administration period starting at about 10.00 a.m.
- Battery of functions tested: Functional observational battery: Passive observations without disturbing the animals, followed by removal from the home cage (posture, tremor, convulsions, abnormal movements, impairment of gait, other findings), open field observations in a standard arena (behavior when removed from cage, posture, tremors, convulsions, abnormal movements, impairment of gait, activity/arousal level, number of rearings within two minutes) and sensorimotor tests as well as reflex tests (approach response, touch response, vision ("visual placing response"), pupillary reflex, pinna reflex, audition ("startle response"), coordination of movements ("righting response"), behavior during "handling", vocalization, pain perception ("tail pinch"), grip strength of forelimbs, grip strength of hindlimbs, landing foot-splay test). The findings were ranked according to the degree of severity, if applicable. The observations were performed at random.
Motor activity was measured an the same day as FOB was performed and at the end of the recovery period. The measurement was performed in the dark using the Multi-Varimex-System (Columbus Instruments Int. Corp., Ohio, USA) with 4 infrared beams per cage. During the measurement the animals were kept in Polycarbonate cages with absorbent material. The animals were put into the cages in a randomized order. The measurements started at about 12.45 p.m. in the main groups and at about 2.00 p.m. in the recovery groups. The number of beam interrupts were counted over 12 intervals, each lasting 5 minutes. Measurement did not commence at the same instant for all cages; the period of assessment for each animal started when the first beam was interrupted by pushing the cage into the rack (staggered start). Measurements ended exactly 60 minutes thereafter. During the measurements the animals received no food and no water.

Sacrifice and pathology:
GROSS PATHOLOGY: Yes
all animals

HISTOPATHOLOGY: Yes
Organs (fixed in 4% formaldehyde): all gross lesions, brain, pituitary gland, thyroid glands (with parathyroid glands), thymus, trachea, lungs, heart, liver, spieen, kidneys, adrenal glands, testes/ovaries (with oviducts), uterus/vagina, epididymides, prostate gland, seminal vesicies, stomach (glandular and non-glandular), duodenum, jejunum, ileum, cecum, colon, rectum, urinary bladder, lymph nodes (mandibular and mesenteric), sciatic nerve, bone marrow (femur), eyes, spinal cord (cervical, thoracic and lumbar cord).
Main study: Histopathology using hematoxylin and eosin staining was performed in all organs of animals of the control and high dose group. Additionally the kidneys of animals of both sexes and the livers of males of the low and mid dose groups were examined. A Mallory staining of the the kidneys of the males of all groups of the main study was performed to detect a2u globulin accumulation.
Recovery study: animals of the control and high dose group were examined for kidney lesions (both sexes: hematoxylin and eosin staining, Mallory staining only in males) and heart lesions (hematoxylin and eosin staining, only males).

Other examinations:
Determination of body weights and following organ weights: liver, kidneys, adrenal glands, testes, epididymides, ovaries, uterus, spleen, brain, heart, thymus
Statistics:
Main group: for most data non-parametric one-way analysis was performed using KRUSKAL- WALLIS test (two-sided). If the resulting p-value was equal or less than 0.05, a pairwise comparison of each dose group with the control group was performed using the WILCOXON test for the hypothesis of equal medians For body weight changes and food consumption: A comparison of each group with the control group was performed using DUNNETT's test (two-sided) for the hypothesis of equal means.

Recovery group: Pairwise comparison of each dose group with the control group was performed using the WILCOXON test for the hypothesis of equal medians, the two-sided Welch t-test or fisher's exact test for the hypothesis of equal proportions.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
no effects observed
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
effects observed, treatment-related
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL CHEMISTRY
At the end of the administration period serum enzyme examination revealed a slight, but statistically significant, increase in alanine aminotransferase activity in the high dose females (0.62 +/- 0.08 µkat/l vs. 0.5 +/- 0.06 in controls). Moreover, significantly increased values for cyanide-insensitive palmitoyl-CoA¬oxidation were found in the liver homogenates of the high dose males (7.20 +/- 0.69 mU/ mg Prot. vs. 5.84 +/- 0.70) and mid and high dose females (5.10 +/- 0.62 and 6.81 +/-1.39 mU/ mg Prot. vs. 3.71 +/-0.37 in controls. The test compound administered did not affect the other serum enzymes. After cessation of treatment all test substance-related findings were reversible.
After 4 weeks of test substance administration blood chemistry determinations showed significantly decreased albumin concentrations in the serum of the high dose males (33.67 +/- 1.56 g/l vs. 35.60 +/- 1.38 in controls). In the serum of the high dose females lower total protein (60.65 +/- 1.17 g/l vs. 63.79 +/-2.29 in controls) and globulin levels (25.26 +/-0.99 g/l vs. 27.39 +/-0.90 in controls) were detected. No test compound-related changes were seen in the other blood chemistry parameters. During the treatment-free recovery period the albumin and total protein concentrations normalized. The globulin levels in the high dose females, however, were reduced further on (27.78 +/-1.43 g/l vs. 29.97 +/-1.90 in controls).

URINALYSIS
At the end of the administration period mid and high dose males as well as high dose females produced increased amounts of urine with decreased specific gravity. Increased blood was also found in the urine specimens of the mid and high dose males and most of the urine samples collected from the high dose males appeared cloudy. Furthermore, microscopic examination of the urine sediments of the mid and high dose males revealed increased numbers of renal tubular epithelial cells, transitional epithelial cells, squameous epithelial cells, granular casts and epithelial cell casts at the end of the administration period. lncreased numbers of transitional epithelial cells were also detected in the urine samples of the low dose males. Most of the transitional epithelial cells found in the urine sediments of the males were degenerated. All effects seen in the urine specimens of the male and female animals were reversible following cessation of test compound administration.


NEUROBEHAVIOUR
No substance-related findings were obtained in the Functional Observational Battery. Regarding the overall motor activity (summation of intervals 1 - 12), a significantly decreased value was seen in females of group 3 (high dose group). This observation was assessed as related to treatment. At the end of the recovery period there were no significant deviations between treated and control animals.
Comparing the single intervals with the control groups, there were statistically significantly increased values in male animals of group 2 (mid dose) and 3, only in interval 3. As no substance-related influence were obtained concerning the overall motor activity in males of the above-mentioned dose groups and due to the single observations, these findings were assessed as being incidental in nature.
In female animals of group 1 (low dose group), a statistically significantly increased value was measured in interval 9, only. Due to the isolated occurrence, this observation was assessed as beeing not related to treatment.
In female animals of the high dose group some isolated decreased values were observed. These impaired values caused the above-mentioned significantly decreased overall motor activity in females of group 3 and were therefore assessed as related to treatment.
At the end of the recovery period no substance-related findings were obtained.


ORGAN WEIGHTS
Absolute weights:
MAIN STUDY: The mean liver weight was slightly although significantly increased in males of the high dose group (+19%). This was regarded treatment-related. The mean kidney weight was significantly increased in males of the high dose group (+26%). This was also regarded treatment-related.
The other mean absolute weight parameters of the animals of the main group did not show significant differences when compared with the concurrent control group.
RECOVERY GROUP: The mean weight of the kidneys was slightly (+10%) although significantly increased in males of the high dose group. This was regarded treatment-related.

Relative weights (related to terminal body weight):
MAIN STUDY: In the high dose group, the mean liver weight was significantly increased in males (+17%) and in females (+22%). This was regarded treatment-related. The mean kidney weights were significantly increased in the high and mid dose groups of males (+11% or +24%, respectively) and in females (+9% or +12%, respectively). This was also regarded treatment-related. In females of the low dose group, the mean weight of the spieen was slightly although significantly increased (+21%). This was regarded fortuitous. The other mean relative weight parameters (when related to terminal body weight) of the animals of the main group did not show significant differences when compared with the concurrent control group.
RECOVERY GROUP: The mean weight of the kidneys was (+15%) significantly increased in males of the high dose group. This was regarded treatment-related. The mean weight of the heart was slightly (+13%) although significantly increased in males of the high dose group. This was not regarded treatment-related.


HISTOPATHOLOGY: NON-NEOPLASTIC
MAIN STUDY: Treatment-related microscopic findings were recorded in the kidneys of male rats (all dose groups) and in the liver of male (high dose group) and female rats (mid and high dose groups).
Slight to severe diffuse accumulation of a2u-globulin in the epithelia — partly also in the tubular lumina — of the proximal tubules of the kidneys was noted in almost all treated males, showing an increase in the graded severity with increasing dosages. Only animal No. 15 of the low dose group revealed a more (multi)focal accumulation of the protein, by this indistinguishable from the control animals. Control animals had only focal accumulations of a2u-globulin, graded slight in three rats and moderate in one rat. No a2u-globulin accumulation worth mentioning was recorded in animal No. 1 of the control group. While the focal accumulation of a2u-globulin reflects the physiologic condition, the diffuse accumulation was interpreted treatment-related.
Further, in two high and one mid dose male, (multi)focal tubular dilation was noted at the cortico-medullary junction in a few (grade 2) or a moderate number (grade 3) of tubules. These were slightly distended — exhibiting a 3- to 4fold tubular diameter — and they were filled with an amorphous proteinaceous material that did not show the tinctorial properties of the a2u-globulin. The material was interpreted to represent cellular detritus of dead tubular cells.
The a2u-globulin accumulation in the kidneys of male rats explained — at least partly — the significantly increased mean absolute (high dose group) and relative (mid and high dose groups) kidney weights.
Further, the following incidental microscopic findings were recorded in the kidneys of male and/or female rats: unilateral cysts(s), individual basophilic tubules in the cortex, (multi)focal calcification in the cortico-medullary area and dilation of the renal pelvis. However, none of these findings could be correlated with the significantly increased mean relative kidney weights (mid and high dose groups) in female rats.
In the liver of female rats of the high and mid dose groups, minimal to moderate fatty infiltration of the hepatocytes in the acinar periphery (zone 1 according to Rappaport) was observed in all but one animal (No. 49 of the mid dose group), with minimal grades of severity in the mid dose group and slight to moderate grades in the high dose group. This finding was interpreted to be treatment-related. Slight fatty infiltration of the hepato¬cytes in the acinar periphery occurred also in one high dose male rat. There were no other treatment-related changes in the hepatocytes of treated male or female animals. Further, the following incidental microscopic findings were recorded in the liver of male and/or female rats: individual small granuloma or (multi)focal vasculitis/perivasculitis in individual triades of Glisson. However, none of these findings could be correlated with the significantly increased absolute (males) and relative (males and females) liver weights in the high dose group.
Additional microscopic findings were noted in the adrenal cortex (extracortical nodule), epididymides (spermatogenic granuloma), lungs (focal lymphoid cell infiltration or intra¬alveolar bone spicules), testes (vacuolization of Sertoli cells), thyroid glands (ectopic thymus) and uterus (dilation of homs). They were either single observations, or they occurred in control animals only, or they were recorded at comparable incidence and graded severity in control and high dose males and/or females, thus giving no indication of a relationship to treatment.

RECOVERY GROUP: In the kidneys, slight to moderate (multi)focal accumulation of a2u-globulin in the epithelia of the proximal tubules of the kidneys was noted in each three treated and control males, showing no difference as well in the incidence as in the graded severity. However, in two high dose males, (multi)focal tubular dilation was noted at the cortico-medullary junction in a few (grade 2) or a moderate number (grade 3) of tubules. These were slightly distended — exhibiting a 3- to 4fold tubular diameter — and they were filled with an amorphous proteinaceous material that did not show the tinctorial properties of the a2u-globulin. The material was interpreted to represent cellular detritus of dead tubular cells. In addition, few or moderate numbers of basophilic tubuli were recorded in four of five high dose males. As well tubular dilation as basophilic (regenerating) tubules were interpreted to be treatment-related. However, these findings did not fully explain the significantly increased mean absolute and relative kidney weights.
Finally, the following incidental microscopic findings were recorded in the kidneys of male and/or female rats: (multi)focal calcification in the cortico-medullary area and chronic progressive nephropathy in a high dose male rat.

Effect levels

open allclose all
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: see 'Remark'
Dose descriptor:
NOAEL
Effect level:
50 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: see 'Remark'

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Due to the findings the target organs were liver and kidneys in both sexes.
In male animals adverse kidney effects were noted at 10 mg/kg bw/day and above. No complete recovery was obtained after cessation of 200 mg/kg bw/day in males. However, these findings (a2u globulin-induced nephropathy) are specific for male rats and therefore have no relevance for humans.
In female animals no signs of toxicity were observed at 10 mg/kg bw/day. The observed findings at 50 mg/kg bw/d (minimal fatty infiltration of liver and increased kidney weights in females) are not considered to be adverse: An increase in cyanide-insensitive palmitoyl-CoA-oxidation in liver is indicative of species-specific peroxisome proliferation. Therefore the accompanying minimal liver effects at this dose (fully reversible) are also not regarded to be of relevance for human risk assessment. The increased kidney weights in females (reversible and without concomitant histological alterations even at the highest dose tested) are also not regarded as adverse effect. Therefore, the NOAEL of this study is considered to be 50 mg/kg bw/d, based on the decreased motor activity (females) and increased liver weights (both sexes) as well as alterations in clinical chemistry and urinalysis parameters (both sexes).
Executive summary:

The test substance (purity 94.9%) was administered to male and female Wistar rats by gavage for 4 weeks at dose levels of 0 (vehicle control), 10, 50 and 200 mg/kg body weight/day as aqueous solution of 0.1% Cremophor EL.

 

Control and high dose groups consisted of each 10 animals per sex, whereas low and mid dose groups consisted of each 5 animals per sex. 5 animals per sex of all dose groups were sacrificed at the end of exposure (main groups). The remaining 5 animals per sex of control and high dose groups were maintained for another 14 days without administration of the test substance (recovery groups).

 

Kidney effects were seen in males of all dose groups (dose-related effect). This was attributed to the sex and species-specific hydrocarbon-induced a2u globulin accumulation in the kidneys of male rats and regarded as not relevant for humans. No effects apart from nephrotoxicity in males no effects at all were seen in females at 10 mg/kg bw/d.

At 50 mg/kg bw/d, reversible fatty infiltration of liver cells were observed in females (4 out of 10 animals) as well as an increase in cyanide-insensitive palmitoyl-CoA-oxidation, which is indicative of species-specific liver peroxisome proliferation. Females showed increased kidney weights (reversible, without histological kidney alterations)

At 200 mg/kg bw/d, peripheral fatty infiltration of liver cells was increased in femals (all animals) and observed also in one male. These effects were reversible. In this dose group the following effects were observed additionally: decreased motor activity (females) and increased liver weights (both sexes) as well as alterations in clinical chemistry and urinalysis parameters (both sexes). Except the kidney lesions in male rats and decreased serum globulin levels in females, no treatment-related effects were reported in the recovery group. Based on the effects observed in the 50 mg/kg bw/d dose group (minimal fatty liver degeneration in female rats) this dose was considered to be the LOAEL by the authors. The authors derived a NOAEL of 10 mg/kg bw/d from this study (BASF AG, 2002).

Remark: Although the authors of this study derived a LOAEL of 50 mg/kg/d, this dose is considered to be a NOAEL: the minimal liver effects in females at this dose are accompanied by signs of liver peroxisome proliferation, a species-specific effect in rodents. Moreover these effects were completely reversible. Increased kidney weights in females are also reversible and occured without any histological alterations in the kidneys, even at the highest dose tested. Therefore, the NOAEL of this study (BASF, 2002) is considered to be 50 mg/kg bw/d. This well performed guideline study (OECD 407) is considered to be of high reliability (RL1).