Dibutylbis(pentane-2,4-dionato-O,O')tin

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

05.10.93 - 25.11.93

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1994

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Dibutyltin dichloride

EC Number:

211-670-0

EC Name:

Dibutyltin dichloride

Cas Number:

683-18-1

IUPAC Name:

dibutyltin dichloride

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Male and female rats of the Wistar Crl:CD (Wi) BR strain were obtained from a "specific pathogen free" colony at Charles River Wiga GmbH, 97633 Sulzfeld, Germany.
- Age at study initiation: 8-9 weeks old
- Weight at study initiation: Females: 179-249 g
- Housing: The female rats were housed individually in solid floor macrolone cages with stainless steel lids of type III (dimensions: 420 mm x 260 mm x 150 mm). In deviation from the study protocol, the animals were not housed in macrolone cages of type II.
Autoclaved sawdust was provided for bedding (supplied by J. Brandenburg, 49424 Goldenstedt, Germany). The cage bottoms and bedding were changed three times weekly. The bedding material is analysed every 6 months for specified contaminants.
- Diet (e.g. ad libitum): Throughout the study, the rats were allowed free access to food. The basic diet used was obtained in powdered form (Ssniff Spezialdiaten GmbH, 59494 Soest, Germany)
- Water (e.g. ad libitum): Tap water was available ad libitum from plastic water bottles attached to each cage
- Acclimation period: The animals used for the study were acclimatized to the laboratories for at least 7 days prior to the start of the mating.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25 °C
- Humidity (%): 30 to 70%
- Photoperiod (hrs dark / hrs light): The animals were exposed to a constant artificial (fluorescent) light cycle of 12 hours light (6.00 to 18.00 hours) and 12 hours dark.


IN-LIFE DATES: From: 08.10.93 To: 05.11.93

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

olive oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The test article was prepared daily as a solution in the vehicle.


VEHICLE
- Justification for use and choice of vehicle (if other than water): nda
- Concentration in vehicle: Rats received dibutyltin dichloride by oral gavage at dosages of 1.0, 2.5, 5.0 and 10 mg/kg daily for 10 consecutive days from day 6 to 15 post-coitum, inclusive.
- Amount of vehicle (if gavage): nda
- Lot/batch no. (if required): 11748, supplied by Henry Lamotte, 28197 Bremen, Germany.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

During the first week of treatment (on 11.10.1993) and at the end of the treatment period (on 16.11.1993), samples of at least 10 ml were taken from each test article formulation together with a reference sample for the control group for determination of concentration, deep-frozen immediately after sampling and sent to Ciba Additive GmbH, D-68619 Lampertheim, Germany for analysis.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 4:1
- Length of cohabitation: During the night
- Verification of same strain and source of both sexes: Yes
- Proof of pregnancy: Vaginal plug/sperm in vaginal smear referred to as day 0 of gestation

Duration of treatment / exposure:

The test material was fed by oral gavage to the rats for 10 consecutive days.

Frequency of treatment:

Daily for 10 days

Duration of test:

20 days, on day 20 the rats were sacrificed

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
1.0 mg/kg/day
Basis:
analytical conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
2.5 mg/kg/day
Basis:
analytical conc.

Doses / concentrations 3

Remarks:

Doses / Concentrations:
5.0 mg/kg/day
Basis:
analytical conc.

Doses / concentrations 4

Remarks:

Doses / Concentrations:
10.0 mg/kg/day
Basis:
analytical conc.

No. of animals per sex per dose:

25 females per dose to allow 20 pregnant females per group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
The dose levels were selected by the study sponsor according to the results of previous studies of Ema et al.
- Rationale for animal assignment (if not random):
Immediately after mating female animals were allocated to treatment groups using a random table of the letters A to E representing the groups 1 to 5.
By use of this random table, the sequence in which successfully inseminated animals were assigned to treatment groups was predetermined.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were examined twice daily at the beginning and end of the working day for morbidity and mortality.


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All animals were examined daily for signs of ill health or overt signs of toxicity, and each finding was recorded.


BODY WEIGHT: Yes
- Time schedule for examinations: The body weight of each inseminated female rat was recorded on days 0, 6, 9, 12, 16 and 20 post-coitum.


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Not a feeding study
- Food consumption: The food consumption of each inseminated female rat was recorded and evaluated for the intervals from day 0 to 6, 6 to 9, 9 to 12, 12 to 16 and 16 to 20 post-coitum.


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: Thymus, liver, bile duct and mesenteric lymph nodes

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
The ovaries and uteri were removed and examined from all females and the following data recorded:
- pregnancy status
- number of corpora lutea in each ovary
- number and position of implantations subdivided into:
a. early resorptions
b. late resorptions
c. dead fetuses
d. live fetuses

Intra-uterine deaths were classified as follows:
- Early resorptions showed decidual or placental tissues only.
- Late resorptions showed embryonic or fetal tissue in addition to placental tissue but excluded fetuses dying in utero within approximately 2 days prior to the terminal kill.
- Dead fetuses included only the fetuses dying in utero within approximately the last 2 days.

The uteri of apparently non-pregnant females were immersed in a 10 per cent solution of ammonium sulphide to reveal evidence of implantation.

Fetal examinations:

The fetuses were killed by an intrapulmonal injection of Eutha 77 (pentobarbitone sodium, Coopers Tierarzneimittel GmbH, 30938 Burgwedel, Germany).
For each live fetus and, if possible, for each dead fetus, the following data were recorded:

- individual placental weight
- external fetal abnormalities
- individual fetal weight
- fetal sex
- skeletal or visceral fetal abnormalities

Approximately half of the fetuses from each litter were eviscerated and the carcasses processed for skeletal examination (Alizarin staining technique).
The remaining fetuses were fixed in ethanol and examined for visceral abnormalities using a modified Wilson-Barrow technique.

Dead fetuses were evaluated separately, if applicable. Structural deviations were classified as follows:

Malformation: rare and/or probably lethal, e.g. hydrocephaly
Variation: changes which regularly occur also in control groups and which are not of functional significance

Statistics:

The statistical evaluation was performed with the standard software package SAS (Statistical Analysis System, release 6.04) excluding the analysis for body weight, body weight change and food consumption, which was performed with the statistical package of the on-line data collection system TERASYS.

Indices:

Data were processed where appropriate to give mean values, group mean values, standard deviations and reproductive indices.

Group mean calculations were normally based on individual data, except for group mean fetal weights where calculations were based on litter means.Group mean values for implantations, intra-uterine deaths and post-implantation losses were calculated in two ways:
Value 1 - all surviving animals that provide evidence of pregnancy including those showing total intra-uterine deaths.
Value 2 - all animals with at least one live fetus at termination.

All values expressed as a percentage were first calculated within the litter and then summarized per group as the mean of individual litter percentages.

Historical control data:

nda

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
No mortalities were observed in the study groups.
No treatment-related clinical signs were observed.
Minor changes such as thinness, bloody incrusted nose, injury at snout, extremities, trunk or skull/ear or hair loss were seen in a few animals of all dose groups on single days.
Necropsy did not reveal any treatment-related findings. Minor findings in the kidneys or liver were observed in a few animals of all study groups.
The mean weight of the thymus was significantly reduced in group 5 (10.0 mg/kg) and is considered to be related to treatment.
Pre-implantation and post-implantation loss was not affected by treatment.
The mean number of fetuses per litter was comparable in all groups. The fetal sex distribution was similar in all groups.
The mean fetal weight and the mean placental weight were not affected by treatment.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
The incidence of fetuses showing malformations was increased in group 5 (10.0 mg/kg). Four fetuses of three litters had malformations. In one fetus an edema was observed. The remaining three fetuses showed more severe malformations. One showed externally ankyloglossia and viscerally an internal hydrocephaly, anophthalmia and diaphragmatic hernia. In the second fetus an agnathia was seen externally and at skeletal examination absence of mandibles and malformed zygomatic arches were observed. At skeletal examination, the third fetus, with a filamentous and curly tail, showed a scoliosis and due to the tail anomaly absence of sacral and caudal vertebrae and sacral vertebral arches.
This low incidence and the lack of a consistent type of malformation render this finding of equivocal toxicological significance.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Administration of dibutyltin dichloride by oral gavage from day 6 to 15 of gestation at a dose level of 10 mg/kg elicited maternal toxicity (reduced body weight gain and food consumption, and thymus atrophy).

Although the incidence of fetuses with malformations was slightly increased at 10.0 mg/kg, this was due to three fetuses in two litters. This low incidence and the lack of a consistent malformation render this finding of equivocal toxicological significance.

Administration of dibutyltin dichloride at a dose level of 5.0 mg/kg elicited slight maternal toxicity (slightly reduced body weight gain and possible thymus atrophy), but did not elicit embyrotoxicity or teratogenicity.

Administration of dibutyltin dichloride at a dose level of 2.5 mg/kg revealed a slightly increased incidence of animals showing thymus atrophy at histopathological examination, but did not elicit embyrotoxicity or teratogenicity.

Administration of dibutyltin dichloride at a dose level of 1.0 mg/kg did not elicit maternal toxicity, embyrotoxicity or teratogenicity.

Applicant's summary and conclusion

Conclusions:

In the oral (gavage) teratogenicity study in the rat the test material was determined, by Parametrix, to have a NOAEL of 1.0 mg/kg bw/day for maternal toxicity and 5.0 mg/kg bw/day for teratogenicity.

Executive summary:

In the oral (gavage) teratogenicity study in the rat (HD project number: 380 -211) the test material was determined, by Parametrix, to have a NOAEL of 1.0 mg/kg bw/day for maternal toxicity and 5.0 mg/kg bw/day for teratogenicity.

This study was conducted in accordance with the "EEC Council Recommendations of 26.10.1983 Concerning Tests Relating to the Placing on the Market of Proprietary Medicinal Products (83/571/EEC)", the "OECD Guidelines for Testing of Chemicals, No. 414, May 12, 1981", the "OECD Principles of Good Laboratory Practice (1981)" and the "Good Laboratory Practice Regulations" as outlined in the "German Chemical Law (Bundesgesetzblatt I, 22.03.1990)".

No mortalities were observed in the study groups.

No treatment-related clinical signs were observed.

Minor changes such as thinness, bloody incrusted nose, injury at snout, extremities, trunk or skull/ear or hair loss were seen in a few animals of all dose groups on single days.

Necropsy did not reveal any treatment-related findings. Minor findings in the kidneys or liver were observed in a few animals of all study groups.

The mean weight of the thymus was significantly reduced in group 5 (10.0 mg/kg) and is considered to be related to treatment.

Pre-implantation and post-implantation loss was not affected by treatment.

The mean number of fetuses per litter was comparable in all groups. The fetal sex distribution was similar in all groups.

The mean fetal weight and the mean placental weight were not affected by treatment.