1,3-diethenyl-1,1,3,3- tetramethyldisiloxane and its platinum(0) complexes

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

In a combined repeated-dose toxicity study with reproduction/developmental toxicity screening test, conducted according to OECD Test Guideline 422 and to GLP, 'Karstedt Concentrate’ was administered daily (in corn oil) by gavage to groups of rats (10/sex/dose) for at least 28 days (males) and 49 -62 days (females) at 30, 125 or 500 mg/kg bw/day. Parental (P0) effects were observed (including reduced food consumption and growth, and haematological and clinical chemistry changes). No adverse effect on the fertility index, the gestation index, the precoital time or the gestation length was reported, resulting in a NOAEL of 500 mg/kg bw/day for fertility and reproductive performance of the P0 generation (Hansen, 2017).

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Remarks:

Part of a combined repeated dose study (OECD 422) with reproductive and developmental toxicity screening.

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August 2016-March 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Crj: CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source:
Charles River Laboratories Germany, Sandhofer Weg 7, 97633 Sulzfeld, Germany.
- Females (if applicable) nulliparous and non-pregnant:
Yes.
- Age at study initiation:
Males and females were aged 81 days at first test material administration.
- Weight at study initiation:
Males: 407.0 - 474.3 g at first test material administration.
Females: 222.7 - 304.2 g at first test material administration.
- Fasting period before study:
Not specified.
- Housing:
Males and females kept in individual cages, except during mating period (see reproductive toxicity
section for further details).
- Diet (e.g. ad libitum):
Standard commercial feed ad libitum.
- Water (e.g. ad libitum):
Tap water ad libitum.
- Acclimation period:
6 days.
ENVIRONMENTAL CONDITIONS
- Temperature (°C):
22°C (+/- 3°C)
- Humidity (%):
55% (+/- 15%)
- Air changes (per hr):
Not specified.
- Photoperiod (hrs dark / hrs light):
12 hrs light (150 lux)/12 hrs dark.
IN-LIFE DATES:
Males: end of the in-life period: 22 September 2016
Females: end of the in-life period: 17 October 2016.

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Formulations were continuously stirred until the last animal of each group had been dosed.
VEHICLE
- Justification for use and choice of vehicle (if other than water):
Corn oil. No justification specified (standard vehicle).
- Concentration in vehicle:
Not specified.
- Amount of vehicle (if gavage):
Constant dose volume of 5 mL/kg bw/day/animal.
- Lot/batch no. (if required):
Caesar and Loretz GmbH, Germany. Batch numbers 15296404 and 15296406.

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: until pregnancy, or 2 weeks.
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy

- Further matings after two unsuccessful attempts: Not specified
- After successful mating each pregnant female was caged (how): individually
- Any other deviations from standard protocol: No.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of each dose solution were analysed by ICP-OES for platinum content, at dates throughout the study period.

Duration of treatment / exposure:

Males and females were dosed from 2 weeks prior to mating and during the mating period.
Males were further dosed after the mating period for a total treatment duration of at least 28 days.
Females were dosed throughout gestation and at least up to and including day 13 post-partum (total of 49-62 days).

Frequency of treatment:

Daily

Details on study schedule:

Not applicable

Dose / conc.:

30 mg/kg bw/day (nominal)

Dose / conc.:

125 mg/kg bw/day (nominal)

Dose / conc.:

500 mg/kg bw/day (nominal)

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
Doses selected on the basis of a 14-day range-finding study (see Supporting study in this endpoint).
- Rationale for selecting satellite groups:
Satellite groups (5/sex/group) were administered vehicle only or the high dose (500 mg/kg bw/day) for 28 days. Blood samples were taken prior to the final dose, and at 3, 6, 12 and 24-hours post administration. Plasma was analysed for elemental platinum as an analytical marker for the test compound (analysis carried out by Allessa, and included as an appendix to the study report). Blood taken from these animals was also assessed for micronucleus formation (see in vivo Micronucleus ESR for full details).

Positive control:

None.

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes.
- Time schedule: At least once daily.
- Cage side observations included: skin/fur, eyes, mucuous membranes, respiratory and circulatory systems, somatomotor activity and behaviour patterns.
DETAILED CLINICAL OBSERVATIONS: Yes.
- Time schedule: At least once daily.
BODY WEIGHT: Yes.
- Time schedule for examinations: On the first day of dosing, weekly thereafter, and at termination.
During gestation, females were weighed on days 0, 7, 14 and 20, and within 24 hours of parturition.
FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes.
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Not specified.
FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Not specified.
WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Monitored daily by visual appraisal.

OTHER: see Repeated dose toxicity for details of other examinations.

Oestrous cyclicity (parental animals):

Yes; determined by evaluating vaginal smears and confirmed by microscopic examination at necropsy.

Sperm parameters (parental animals):

Parameters examined in male parental (F0) animals:
Weights of testes, epididymes, and combined weight of prostate/seminal vesicles/coagulating glands, and histopathological examination of the same. A detailed examination of the qualitative stages of spermatogenesis.

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: Yes, following a randomisation scheme.
- 8 top 10 pups/litter; excess pups (at least 2, preferably female) were killed and discarded.

PARAMETERS EXAMINED
The following parameters were examined in offspring:
Number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities, anogenital distance (AGD), presence of nipples/areolae in male pups, thyroid hormone levels (T4).

GROSS EXAMINATION OF DEAD PUPS:
Yes. Dead pups and pups sacrified at day 13 post-partum were carefully examined externally for gross abnormalities. External reproductive genitals were examined for signs of altered development. The thyroid from 1 male and 1 female pup/litter was weighed and fixed for histopathological examination.

ASSESSMENT OF DEVELOPMENTAL NEUROTOXICITY: Not examined.

ASSESSMENT OF DEVELOPMENTAL IMMUNOTOXICITY: Not examined.

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals were sacrificed on test day 52 (approximately 2 weeks post-mating, for a total of 37 treatment days).
- Maternal animals: All surviving animals were sacrificed on day 13 post-partum (between test days 66 and 77, for a total of 51-62 treatment days).

GROSS NECROPSY
All tissues and organs were examined macroscopically.

HISTOPATHOLOGY / ORGAN WEIGHTS
The weight of the following organs was recorded before fixation (where applicable):
Adrenals, kidney (2), epididymis (2), liver, uterus (incl. cervix), ovary (2), spleen, testicle (2), thyroid, thymus, combined weight of prostate+seminal vesicles+coagulating glands. Paired organs were weighed individually and identified as left or right.

The brain and heart of 5 animals/sex/group were also weighed.

The following organs/parts were fixed for microscopic examination: adrenal gland (2), bone, bone marrow (os femoris), brain, epididymis (2), eye with optic nerve (2), all gross lesions observed, heart, intestine, kidney and ureter (2), liver, lungs with bronchi and bronchioles, lymph node (1 cervical and 1 mesenteric), mammary gland, skeletal muscle, sciatic nerve, oesophagus, ovary and oviduct, pituitary, prostate/seminal vesicles/coagulating gland, spinal cord (3 sections), spleen, stomach, testicle (2), thyroid, thymus, tissue masses or tumours, tongue, trachea, urinary bladder, uterus (incl. cervix), vagina.

Postmortem examinations (offspring):

SACRIFICE
- All F1 animals were sacrificed on day 13 post-partum.

GROSS EXAMINATION OF DEAD PUPS:
Yes. Dead pups and pups sacrified at day 13 post-partum were carefully examined externally for gross abnormalities. External reproductive genitals were examined for signs of altered development. The thyroid from 1 male and 1 female pup/litter was weighed and fixed for examination.

Statistics:

Homogeneity of variances and normality of distribution were tested using the Bartlett's and Shapiro-Wilks test. In case of heterogeneity and/or non-normality of distribution, Anova and Dunnet's test were used. Non-parametrical values were evaluated using the Fisher or Chi-squared tests.

Reproductive indices:

Male fertility index (%): 100 x (Males with confirmed female insemination/number of rats used).
Female fertility index (%): 100 x (Pregnant rats/total rats).
Gestation index (%): 100 x (Dams with live pups/pregnant rats).

Offspring viability indices:

Birth index (%): 100 x (Total pups born {alive or dead}/number of implantation scars).
Live birth index (%): 100 x (Number of pups alive on day 0/1 of lactation/total number of pups {alive or dead}).
Viability index (%): 100 x (Pups alive on day 4/Pups alive on day 0/1).
Pre-implantation loss (%): 100 x ((Corpora lutea - implantations)/corpora lutea).
Post-implantation loss (%): 100 x ((Implantations - living foetuses)/implantations).

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

All males of the high-dose group displayed increased salivation, considered to be treatment-related and adverse.
4/10 high-dose females also displayed increased salivation, also considered to be treatment-related and adverse.

Description (incidence and severity):

not applicable

Mortality:

mortality observed, treatment-related

Description (incidence):

Males:
500 mg/kg bw/day: no deaths.
Females:
500 mg/kg bw/day: One premature death (during lactation period).

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Males:
500 mg/kg bw/day: significantly lower body weight than control during the whole study period (e.g. 6.5%, 11.5% and 14.4% below controls on test days 22, 29 and 52, respectively).
Females:
500 mg/kg bw/day: no effects on body weights pre-mating or during lactation.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

FOOD CONSUMPTION
Males
500 mg/kg bw/day: lower food consumption week 1 of study, approximately half control value.
125 mg/kg bw/day: lower food consumption week 1 of study, approximately 15% below control value.
Food consumption normalised between test days 22 and 28, so these observations were not considered to be adverse.

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Males:
Group mean white blood cell (WBC) counts (absolute values) were higher than the control mean for all treated groups, but the effect only achieved statistical significance at 500 mg/kg bw/day. These increases were particularly associated with dose-related elevations in mean neutrophil and lymphocyte counts (absolute values), which were themselves statistically significant at the high-dose level. For the high-dose group, statistically significant increases in monocytes and large unclassified cell means were also noted. A dose-related decrease in the mean reticulocyte (%) counts was evident for all treated groups when compared to the respective control mean. A statistically significant difference was present only at 125 and 500 mg/kg bw/day, although the effect in the mid-dose fell within historical control ranges for this effect (and, as such, was not considered by the study authors to be related to treatment)

Females:
Mean white blood cell (WBC) counts (absolute values) showed minor increases at the mid- and high-dose (although neither value achieved statistical significance), and which again appeared to be primarily related to limited increases in neutrophil and lymphocyte group mean values.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Males:
Increases in group mean alanine aminotransferase (ALAT) values were noted for all treated groups, which achieved statistical significance at 125 and 500 mg/kg bw/day. However, the magnitude of this effect was limited in degree (only the high-dose value approached the upper boundary of the historical control dataset). Clear treatment-related differences in other measured serum enzyme levels were not evident.
Several other statistically significant effects were detected in group mean values at 500 mg/kg bw/day: concentrations of albumin (decrease), total cholesterol (increase), protein (decrease) and calcium (decrease).

Females:
No statistically significant changes were seen in any of the clinical chemistry parameters of females.
There was a dose-related decrease in aP, but statistical significance was not achieved at any dose level.

Urinalysis findings:

not specified

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

Males:
One mid-dose animal showed slight signs of positive geotropism; another had slight diarrhoea. One low-dose and one high-dose animal showed "slight influences" during the wire manoeuvre test, and males in these two groups showed a decreased reaction to a tail pinch. All observations were cons idered to be spontaneous and not related to treatment.

Females:
One mid-dose female was noted with salivation and a slightly reduced urination. This was considered to be spontaneous and not related to treatment.

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Males and females:
500 mg/kg bw/day: Lung - Increased pigment deposition (4/5 males, 2/6 females), haemorrhages (3/5 males, 4/6 females) and granulomatous inflammation (4/5 males, 4/6 females). Incidence of pigment deposition and inflammation was statistically significant in males.
The one female that died during the study period was found to have marked granulomatous inflammation of the lungs. The investigators concluded that the pulmonary effects noted for the male and female animals were considered to be a foreign body response to test item in the lung rather a toxicological effect.

Females:
500 mg/kg bw/day: Statistically significantly increased incidence of hypertrophy of the adrenal cortex in 3/6 females. [Note that there were changes in adrenal organ weight at this dose level.] However, evidence of similar hypertrophic change was not found when tissues from mid-dose group females were examined.
No test item-related microscopic changes in the reproductive organs of high-dose males or females were detected. Qualitative evaluation of the stages of spermatogenesis in males of this treatment group revealed no abnormalities.

Histopathological findings: neoplastic:

not specified

Other effects:

effects observed, treatment-related

Description (incidence and severity):

A limited decrease in Thyroid Hormone T4 concentration (17.5% below the mean value of the control group, p ≤ 0.05) was noted in male animals of the high-dose group. T4 measurements for females of all treated groups were unaffected, as were those for males receiving 30 or 125 mg/kg bw/day.

Reproductive function: oestrous cycle:

no effects observed

Description (incidence and severity):

No test item-related influences on oestrous cycle in any treatment group.

Reproductive function: sperm measures:

no effects observed

Description (incidence and severity):

No test item-related influence was noted on the qualitative stages of spermatogenesis. The histopathological examination performed on one testicle and one epididymis (with special emphasis on the qualitative stages of spermatogenesis (proliferative, meiotic and spermiogenic phases) and histopathology of the interstitial testicular structure) also did not reveal any test item-related effects.

Reproductive performance:

no effects observed

Description (incidence and severity):

No adverse effect on the fertility index, the gestation index, the precoital time or the gestation length in the P0 animals.
[Adverse effects on post-implantation loss and number of stillborn pups discussed below; F1 section.]

Key result

Dose descriptor:

NOAEL

Remarks:

Fertility and reproduction parameters

Effect level:

500 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reproductive performance

Critical effects observed:

not specified

Clinical signs:

not examined

Mortality:

not examined

Body weight and weight changes:

not examined

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

not examined

Clinical signs:

not specified

Description (incidence and severity):

not applicable

Mortality / viability:

mortality observed, treatment-related

Description (incidence and severity):

No differences considered to be related to treatment were noted for the mean number of: corpora lutea; implantation sites; total pups born (alive and dead); live born pups; and the number of stillbirths when comparing the control group to the low and intermediate dose groups (30 or 125 mg/kg bw/day). Related reproductive indices were unaffected. An increased post-implantation loss (dam/group) was observed for all treatment groups. When calculated as a group index [%], the differences achieved statistical significance. In the high-dose group (500 mg/kg bw/day), the post-implantation loss index was clearly above the range of the background historical control data, and was considered to be related to treatment. The respective index for the low-dose group was noted to be within the historical control dataset for this parameter, whilst that for the mid-dose group just exceeded the historical control upper bound. In the case of the latter group the data were skewed due to the influence of a high post-implantation loss for a single animal (no 56). Therefore, it was concluded by the investigators that the post-implantation loss differences observed for the low- and mid-dose groups may have been spontaneous in nature rather than treatment-related. For the high-dose (500 mg/kg bw/day), a statistically significantly decreased live birth index was noted (due to a total of 7 stillbirths from 3 different dams), which was considered to be related to treatment. This was accompanied by lower pup weights [see 'Body weight and weight changes' section (F1)]. A possible effect in relation to decreased mean pup survival was also evident for the high-dose group, but this was due only to the influence of 2 litters (one was lost due to the death of dam, whilst the other was a total litter loss). Survival in the remaining 7 litters at this treatment level was good and similar to that of the control group.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

At 500 mg/kg bw/day, a statistically significant depression in mean pup bodyweight was evident at all timepoints (viz. approximately 15%, 18%, and 32% below control values at d1, d4, and d13, respectively). [data combined for sexes; similar extent of difference in both sexes]

Description (incidence and severity):

not applicable

Description (incidence and severity):

not applicable

Description (incidence and severity):

not applicable

Description (incidence and severity):

not applicable

Description (incidence and severity):

not applicable

Description (incidence and severity):

not applicable

Description (incidence and severity):

not applicable

Description (incidence and severity):

not applicable

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

No difference was noted for the weights of the left and right thyroid glands between the pups of the control group and the pups of the treatment groups.

Gross pathological findings:

no effects observed

Description (incidence and severity):

The external macroscopic examination after sacrifice revealed no test item-related gross abnormalities.

Histopathological findings:

no effects observed

Description (incidence and severity):

No test item-related changes were noted in the thyroid glands of either sex.

Other effects:

effects observed, treatment-related

Description (incidence and severity):

ENDOCRINE PARAMETERS
No effects on offspring endocrine parameters [nipple retention in male pups and anogenital distance in male and female pups].

No notable differences were apparent between control and treated groups in respect of thyroid hormone T4 levels at lactation day (LD) 4. However, by LD 13, a modest reduction in group mean serum T4 level was evident for the pups of dams which received 500 mg/kg bw/day, but not for the pups of the other treated groups. Since the reductions were observed in both male and female pups from the former group, and were statistically significant, this finding was considered to be treatment-related. These changes were not associated with thyroid organ weight effects or adverse histopathological findings.

Description (incidence and severity):

not applicable

Description (incidence and severity):

not applicable

Key result

Dose descriptor:

NOAEL

Remarks:

Pre-natal development (conception to birth)

Generation:

F1

Effect level:

125 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Decreased live birth index and increased post-implantation loss

Key result

Dose descriptor:

NOAEL

Remarks:

Post-natal development of pups

Generation:

F1

Effect level:

125 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

viability

body weight and weight gain

Critical effects observed:

not specified

Clinical signs:

not examined

Mortality / viability:

not examined

Body weight and weight changes:

not examined

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Histopathological findings:

not examined

Other effects:

not examined

Behaviour (functional findings):

not examined

Developmental immunotoxicity:

not examined

Reproductive effects observed:

not specified

Conclusions:

In a combined repeated-dose toxicity study with reproduction/developmental toxicity screening test, conducted according to OECD Test Guideline 422 and to GLP, 'Karstedt Concentrate’ was administered daily (in corn oil) by gavage to groups of rats (10/sex/dose) for at least 28 days in males (during pre-mating, mating and post-mating) or 49-62 days in females (during pre-mating, mating, gestation and lactation) at 30, 125 or 500 mg/kg bw/day. Parental (P0) effects were observed (including reduced food consumption and body weight, and haematological and clinical chemistry changes). The NOAEL for adverse effects on fertility and reproductive performance of the P0 generation was established at 500 mg/kg bw/day, the highest dose tested. In the F0 generation, increased post-implantation loss and increased number of stillborn pups (decreased live birth index), and reduced pup body weights and reduced viability index (increased mortality during lactation), were reported at the highest tested dose, leading to an NOAEL of 125 mg/kg bw/day for adverse effects on pre- and post-natal development.

Executive summary:

In a combined repeated-dose toxicity study with reproduction/developmental toxicity screening test, conducted according to OECD Test Guideline 422 and to GLP, platinum(0) 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes ('Karstedt Concentrate’) was administered daily (in corn oil) by oral gavage to groups of rats (10/sex/dose) for at least 28 days in males (during pre-mating, mating and post-mating) or 49-62 days in females (during pre-mating, mating, gestation and lactation) at 30, 125 or 500 mg/kg bw/day. Control animals received vehicle only.

In the high-dose group, one female died, and reduced body weights were seen in males. On commencement of treatment, food consumption was transiently lower in males in the mid- and high-dose groups, but with a very marginal degree of effect evident for the former. Haematological examination revealed effects on white blood cell parameters mainly in males in the high-dose group. A statistically significant reduction in group mean reticulocyte count was also evident at the high- and mid-dose (though the value for the latter was within the historical control range for this parameter). Statistically significant effects were noted for several clinical chemistry parameters in males receiving 500 mg/kg bw/day, although effect severity was limited. A dose-related increase in absolute and relative adrenal gland weight was seen in females at 125 and 500 mg/kg bw/day (only reaching statistical significance at the higher dose, where histopathology indicated the existence of an accompanying adrenal cortical hypertrophy). Males at the highest tested dose showed a decrease in thyroid hormone T4 concentration, whereas females were unaffected.

 

No adverse effect on the fertility index, the gestation index, the precoital time or the gestation length was reported, resulting in a NOAEL of 500 mg/kg bw/day for fertility and reproductive performance of the P0 generation.

In the F1 generation, increased post-implantation loss and increased number of stillborn pups (decreased live birth index), and reduced pup body weights and reduced viability index (increased mortality during lactation), were reported at the highest tested dose (500 mg/kg bw/day), leading to an NOAEL of 125 mg/kg bw/day for adverse effects on pre- and post-natal development. By lactation day 13, there was a modest reduction in group mean serum thyroid hormone (T4) level evident for the pups of dams which received 500 mg/kg bw/day, but not for the pups of the other treated groups; this finding was considered to be related to treatment, but was not associated with thyroid organ weight effects or adverse histopathological findings.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

500 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Good.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

In a combined repeated-dose toxicity study with reproduction/developmental toxicity screening test, conducted according to OECD Test Guideline 422 and to GLP, platinum(0) 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes ('Karstedt Concentrate’) was administered daily (in corn oil) by oral gavage to groups of rats (10/sex/dose) for at least 28 days (males; during pre-mating, mating and post-mating) or 49-62 days (females; during pre-mating, mating, gestation and lactation) at 30, 125 or 500 mg/kg bw/day. Control animals received vehicle only.

 

In the parental (P0) animals, in high-dose group, one female died and reduced body weights were seen in males. On commencement of treatment, food consumption was transiently lower in males in the mid- and high-dose groups, but with a very marginal degree of effect evident for the former. Haematological examination revealed effects on white blood cell parameters mainly in males in the high-dose group. A statistically significant reduction in group mean reticulocyte count was also evident at the high- and mid-dose (though the value for the latter was within the historical control range for this parameter). Statistically significant effects were noted for several clinical chemistry parameters in males receiving 500 mg/kg bw/day, although effect severity was limited. A dose-related increase in absolute and relative adrenal gland weight was seen in females at 125 and 500 mg/kg bw/day (only reaching statistical significance at the higher dose, where histopathology indicated the existence of an accompanying adrenal cortical hypertrophy). Males at the highest tested dose showed a decrease in thyroid hormone T4 concentration, whereas females were unaffected.

 

No adverse effect on the fertility index, the gestation index, the precoital time or the gestation length was reported, resulting in a NOAEL of 500 mg/kg bw/day for fertility and reproductive performance of the P0 generation (Hansen, 2017).

Effects on developmental toxicity

Description of key information

In a combined repeated-dose toxicity study with reproduction/developmental toxicity screening test, conducted according to OECD Test Guideline 422 and to GLP, 'Karstedt Concentrate’ was administered daily (in corn oil) by gavage to groups of rats (10/sex/dose) for at least 28 days at 30, 125 or 500 mg/kg bw/day. The NOAEL for adverse effects on pre- and post-natal development was 125 mg/kg bw/day, based on an increased post-implantation loss and increased number of stillborn pups, and reduced pup body weights and reduced viability index, at the highest tested dose (Hansen, 2017).

Effect on developmental toxicity: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

125 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Good.

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

In a combined repeated-dose toxicity study with reproduction/developmental toxicity screening test, conducted according to OECD Test Guideline 422 and to GLP, platinum(0) 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes ('Karstedt Concentrate’) was administered daily (in corn oil) by oral gavage to groups of rats (10/sex/dose) for at least 28 days (males; during pre-mating, mating and post-mating) or 49-62 days (females; during pre-mating, mating, gestation and lactation) at 30, 125 or 500 mg/kg bw/day. Control animals received vehicle only.

 

In the F1 generation, increased post-implantation loss and increased number of stillborn pups (decreased live birth index), and reduced pup body weights and reduced viability index (increased mortality during lactation), were reported at the highest tested dose (500 mg/kg bw/day), leading to an NOAEL of 125 mg/kg bw/day for adverse effects on pre- and post-natal development. By lactation day 13, there was a modest reduction in group mean serum thyroid hormone (T4) level evident for the pups of dams which received 500 mg/kg bw/day, but not for the pups of the other treated groups; this finding was considered to be related to treatment, but was not associated with thyroid organ weight effects or adverse histopathological findings.

 

As such, a NOAEL for pre- and postnatal developmental effects in the F0 generation was 125 mg/kg bw/day (Hansen, 2017).

Justification for classification or non-classification

The effects observed and reported in the OECD 422 study on Karstedt concentrate support classification of this substance as Repro. Category 2 (H361d: Suspected of damaging the unborn child), on the basis of increased post-implantation losses, increased numbers of stillbirths and, consequently, reduced live birth index in the mid- and high-dose animals. For post implantation loss, 3/9 dams (dams 71, 73 and 79) were severely affected in the high- dose group (a fourth dam (dam 76) was slightly elevated above the mean, but not to the extent of the other three). Three out of nine dams (dams 71, 73 and 80) showed a reduced live birth index, all other dams were found to have 100% live births. Therefore, only 3/9 dams were affected for each key parameter, but 4/9 dams were affected overall. In the mid-dose group, the results were heavily skewed by a single animal (No. 56, post-implantation loss 64.7%).

In respect of the outcomes of the TG 422 study conducted on Karstedt catalyst, it is considered that the criteria for assignment of a classification as Reproductive toxicant Category 2 are met (on the basis of developmental toxicity, i.e. H361d). It is noted that other registered platinum substances have not been associated with reproductive or developmental effects and although a qualitatively similar pattern of effects was observed for 1,1,3,3- tetramethyl-1,3-divinyldisiloxane (CAS 2627-95-4, the ligand present in Karstedt concentrate) none of the short linear siloxanes are classified for reproductive/developmental toxicity.

A proposal is included in this dossier for further testing to clarify the reproductive/developmental toxicity profile of Karstedt concentrate and, consequently, its most appropriate classification for this endpoint.