Potassium bromide

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

1995

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

EPA OPP 83-3 (Prenatal Developmental Toxicity Study)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: - 83/571/EEC

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: JMAFF No.4200

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Sodium bromide

EC Number:

231-599-9

EC Name:

Sodium bromide

Cas Number:

7647-15-6

IUPAC Name:

sodium bromide

Details on test material:

- Name of test material (as cited in study report): Sodium bromide ´technical grade`
- Description: White crystalline solid
- Analytical purity: 99.84%
- Lot/batch No.: 940045
- Expiration date of the lot/batch: February 1996
- Storage condition of test material: at room temperature in the light
Potassium bromide is an inorganic salt that dissociates to its composite ions in aqueous solutions at environmental pH and temperature. Comparison of the available data on the various bromide salts have shown that the bromide ion is the relevant ion for determination of the toxicological profile with simple cations such as potassium, sodium or ammonium, that are ubiquitous in nature, having little or no influence on the bromide ion properties. It is therefore justified to read-across data from other inorganic bromide salts to potassium bromide.

Test animals

Species:

rat

Strain:

other: Crl: CD BR VAF/Plus

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River UK Limited, Margate, Kent
- Age at study initiation: 8-10 weeks
- Weight at study initiation: 196-259 g (first batch 201-259 g, second batch 196-239 g)

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Dosage volumes were calculated for individual animals on Day 6 of pregnancy and adjusted according to bodyweight on Day 8, 10, 12 and 14.

VEHICLE
- Concentration in vehicle: 0, 10, 30 and 100 mg/mL
- Amount of vehicle (if gavage): 10 mL/kg bw

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The mean achieved concentrations of sodium bromide in formulations prepared on the first and last days of treatment were within 8% of nominal concentrations.

Duration of treatment / exposure:

Days 6-15 post coitum

Frequency of treatment:

daily

Duration of test:

until Day 20 post coitum

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 100, 300 and 1000 mg/kg bw/day
Basis:
actual ingested

No. of animals per sex per dose:

25 females/group

Control animals:

yes, concurrent vehicle

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: on Days 0, 3, 6, 8, 10, 12, 14, 16, 18 and 20 of pregnancy

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- on Days 3, 6, 8, 10, 12, 14, 16, 18 and 20 of pregnancy

POST-MORTEM EXAMINATIONS: Yes
- only two animals were examined; one which died uring the study period and another one which had to be killed for humane reasons.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes

Fetal examinations:

- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [half per litter]
- Skeletal examinations: Yes: [half per litter]

Statistics:

Significance tests, employing analysis of variance followed by an intergroup comparison with the control, were performed on the following parameters and results are presented in relevant table of this report:
bodyweight change, mean food consumption, litter data, sex ratio and foetal abnormalities and variants.
Depending on the heterogeneity of variance between treatment groups, parametric tests, analysis of variance followed by Williams`test or non-parametric tests, Kruskal-Wallis followed by Shirley`s test were used to analyse these data, as appropriate.
For litter data and foetal changes the basic sample unit was the litter, and, due to the preponderance of non-normal distributions, non-parametric analyses were routinely used. Analysis of foetal abnormalities was performed using a trend test on the number of litters affected, followed by a one-tail 2 sample permutation test. All significant (ie p≤0.05) intergroup differences from the control are reported only when supported by a significant analysis of variance (p≤0.05). Where 75% or more of the values for a given variable were the same, a Fisher`s exact test was used.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
Treatment at 1000 mg/kg bw/day was associated with unsteady gait in all animals. This sign was first apparent following administration of the second dose on Day 7 post coitum. Thereafter, all animals showed this sign at daily examination prior to dosing on Day 8-11 inclusive and, after dosing on Days 8-15. From Day 11, although most animals showed unsteady gait prior to dosing on Days 12 and 13, the incidence was lower on Days 14 and 15 with only 12/24 animals showing this signs prior to dosing on Day 15. Although the final dose was administered on Day 15 post coitum, unsteady gait was apparent for 8/24 animals on Day 17.
As the treatment period progressed, additional abnormalities of movement became apparent: all animals showed feet falling through the cage grid floor during ambulation on at least one occasion, and 23 animals showed poorly coordinated movements on at least one occasion. Both of these signs were first apparent after dosing on Day 9 post coitum. In both cases, there was striking difference in the incidence of affected animals prior to dosing as opposed to after dosing: although only 1 or 2 animals showed these signs prior to dosing up to 24 animals showed feet falling through the cage grid floor during ambulation after dosing, and up to 16 animals showed poorly coordinated movements. It was noted that the incidence of poorly coordinated movements was highest towards the end of the treatment period (days 13-15). Following administration of the final dose on Day 15, these signs were not apparent on Days 16-20.
Treatment at 1000 mg/kg bw/day was also associated with reduced bodytone in all animals. This sign was first apparent following administration of the second dose on Day 7 post coitum. During Days 8-15, there was a clear difference in the incidence of affected animals prior to dosing as opposed to after dosing. This difference was most pronounced towards the end of the treatment period (Days 13-15), when only 1 to 4 animals were affected prior to dosing in contrast to 18-24 animals after dosing. Although the final dose was administered on Day 15, reduced bodytone was apparent for 3/24 animals on Day 16 and 1/24 animals on Day 17.
Treatment at 1000 mg/kg bw/day was also associated with hair loss; 22/24 animals showed hair loss compared with 0/25 controls. In all cases, the hair loss was first noted between Day 14 and Day 19 post coitum and in 7 animals was apparent on Day 20 post coitum.
Occasional instances of increased lacrimation, brown staining on fur, periorbital staining and wet staining around the urogenital region were also observed at 1000 mg/kg bw/day.
No clinical signs considered to be attributable to treatment were observed at 100 or 300 mg/kg bw/day.
There was one mortality on the study which was considered to be related to treatment. One animal of the highest dosage group (1000 mg/kg bw/day), was sacrificed for humane reasons prior to dosing on Day 11 of pregnancy. Prior to sacrifice, reduced bodytone, unsteady gait, red periorbital staining, brown staining on fur, poorly coordinated movements, increased lachrymation, wet urogenital staining and bodyweight loss (bodyweight loss of 19 g were recorded between Days 6-8 of pregnancy) were evident. In addition, poorly coordinated movements were observed earlier than for the other animals in the same treatment group. Post mortem examination failed to establish any obvious cause for the physical condition. It is clear evidence that this animal showed a more severe response to treatment compared with the rest of the animals at the same dosage level, all of which survived to termination.
At 1000 mg/kg bw/day, mean bodyweight gain during the first six days of treatment was significantly lower than in controls. Thereafter, mean bodyweight gains during Days 12-16 were comparable to the controls. However, mean bodyweight gains during Days 16-20 were significantly lower than in controls, also after correction of body weight gains for gravid uterus weight.
At 300 mg/kg bw/day, bodyweight gain throughout Days 6-16 was comparable to the controls. However as at 1000 mg/kg bw/day, bodyweight gain during Days 16-20 was significantly lower than in controls. This was also true after correction for gravid uterus weight.
At 100 mg/kg bw/day, there was a slightly increased bodyweight gain compared to controls.
Food consumption of animals treated at 1000 mg/kg bw/day was higher than in controls during the first four days of treatment (differences attained statistical significance for Days 8 and 9), despite the fact that bodyweight gains were significantly lower than in controls during this period. This was reflected in higher food conversion ratios during this period, indicative of impaired efficiency of food utilisation. Food consumption at this dosage was noticeably higher than in controls during Days 14-15 and lower during Days 18-19.
At 100 and 300 mg/kg bw/day, there were no adverse effects on food consumption or food utilisation.
Other than the previously mentioned increased incidence of hair loss in the 1000 mg/kg bw/day group compared with controls, the incidence of findings noted at macroscopic post mortem examination did not indicate any obvious adverse effect of treatment.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

LOAEL

Effect level:

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

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
One female receiving 100 mg/kg bw/day showed total litter loss in utero (total resorption). In view of the absence of similar findings at higher dosages which indicates no dose-response relationship this finding is considered to be co-incidental and unrelated to treatment. The following assessment is based on the 23, 21, 24 and 22 females with live young at Day 20 in Groups 1-4, respectively.
Reproductive performance:
No effects on the reproductive performance, fetal deaths, fetal weight as well as on the sex ratio was evident on comparison of treated groups with concurrent controls.
Skeletal and visceral malformations:
There was a higher incidence of foetuses from the 1000 mg/kg bw/day group showing malformations. These malformations were principally visceral, affecting the urogenital system (i.e. absent left kidney and/or ureter, absent or narrow left uterine horn), and thoracic skeletal malformations manifest as abnormalities of the ribs. No similar malformations were observed in the controls.
At 100 and 300 mg/kg bw/day, the type and incidence of malformations did not indicate any adverse effect of treatment.
Skeletal anomalies and variants:
At 1000 mg/kg bw/day, the incidence and distribution within litter of foetuses with skeletal anomalies was significantly different from that of controls. Minimally distorted ribs were seen in 8 foetuses in 7 litters, another 5 foetuses in 4 litters showed more severe rib anomalies and were classified as malformed. There was and increased incidence of foetuses/litters showing irregular ossification of the thoracic vertebral centra, and shortened/absent 13th ribs. The latter finding being corroborated by a complete absence of foetuses showing supernumerary ribs, a highly unusual incidence. The percentage of foetuses/litters with reduced ossification of the cranial centres was statistically significantly higher than in controls.
At 300 mg/kg bw/day, the incidence and distribution within litters of foetuses with skeletal anomalies was also statistically significantly different from that of controls. The difference was principally due to an increased incidence of foetuses with reduced ossification. In addition, there was a slightly higher percentage incidence of foetuses with variant sternebrae, principally due to an increase in unossified sternebrae. It was noted that only one foetus showed supernumerary ribs. In view of the effects observed at 1000 mg/kg bw/day, these differences are considered to be related to treatment.
At 100 mg/kg bw/day, the type, incidence and distribution of skeletal anomalies and the percentage incidence of supernumerary ribs and variant sternebrae did not indicate any obvious adverse effects of treatment.
Visceral anomalies:
The type, distribution and incidence of visceral anomalies did not indicate any obvious adverse effects of treatment.

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: embryotoxicity

2

Dose descriptor:

LOAEL

Effect level:

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

Basis for effect level:

other: embryotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Table A6.8.1/05-1:    Summary of Adult Performance

Category	Group (Dosage [mg NaBr/kg/day])
	1 (0)	2 (100)	3 (300)	4 (1000)
No. of mated	25	25	25	25
No. of killed (Day 11 of pregnancy)	0	0	0	1
No. of non-pregnant	2	3	1	2
Total litter loss in utero	0	1	0	0
No. with live young at Day 20	23	21	24	22

 

 

 

Table A6.8.1/05-2:    Bodyweights and bodyweight change during pregnancy - dams with live young, group mean values

Group ( [mg NaBr/kg/day])	No. of animals	Bodyweight [g] at Day of pregnancy And (bodyweight change [g]) from Day 6 of pregnancy										Corrected bodyweight (gain) ***
		0	3	6	8	10	12	14	16	18	20
1 (0)	23	222.7 (-47.0)	249.9 (-19.8)	269.7 (0)	281.8 (12.1)	293.4 (23.7)	310.9 (41.2)	325.5 (55.8)	346.0 (76.3)	376.5 (106.8)	414.9 (145.2)	333.4 (63.7)
2 (100)	21	221.1 (-46.8)	248.4 (-19.5)	268.0 (0)	280.5 (12.6)	294.1 (26.2)	312.0 (44.0)	327.9 (59.9)	347.4 (79.4)	379.1 (111.1)	417.9 (149.9)	336 (68)
3 (300)	24	224.2 (-45.6)	249.0 (-20.8)	269.8 (0)	282.5 (12.8)	296.2 (26.5)	312.8 (43.0)	325.5 (55.7)	345.3 (75.6)	369.3 (99.5) *	403.7 (133.9) *	328.2 (58.5)
4 (1000)	22	223.4 (-46.3)	248.5 (-21.2)	269.7 (0)	279.6 (9.9)	284.5 (14.9) **	298.1 (28.4) *	312.9 (43.2) **	333.0 (63.3) **	360.1 (90.4) **	390.7 (121.0) **	316.2 (46.5)

*      statistically different from control with p ≤ 0.05

**    statistically different from control with p ≤0.01

***  bodyweight and bw gain were corrected for gravid uterus weight (bw day 20- gravid uterus weight; bw gain - gravid uterus weight)

 

Table A6.8.1/05-3:    Food consumption during pregnancy - Dams with live young, group mean values [g/rat/day]

Days of pregnancy	Group (Dosage [mg NaBr/kg/day])
	1 (0)	2 (100)	3 (300)	4 (1000)
No. of animals observed:	23	21	24	22
3-5	27	26	25	26
6-7	27	28	28	30
8-9	28	28	29	32*
10-11	28	30	29	28
12-13	30	31	30	31
14-15	31	32	32	36**
16-17	34	34	32	34
18-19	33	34	31	30**

*   statistically different from control with p ≤ 0.05

** statistically different from control with p ≤ 0.01

 

Table A6.8.1/05-4:    Litter data - Group values

Group Dosage [mg NaBr/kg/day])	1 (0)	2 (100)	3 (300)	4 (1000)
Dams with live young
No. of litters	23	21	24	22
Group mean values
No. of corpora lutea	16.2	15.4	15.3	15.7
No. of implantations	14.9	14.6	14.0	14.1
No. ofin uterodeath -                     early -                     late -                     early and late	0.6 0.2 0.8	0.6 0.0 0.6	0.7 0.1 0.8	0.8 0.2 1.0
No. of live young	14.1	14.0	13.1	13.1
Litter weight [g]	53.69	55.0	50.52	49.0
Foetal weight [g]	3.81	3.92	3.84	3.75
Graivid uterine weight [g]	81.48	81.88	75.35	74.46
Sex ratio [%]	48.0	54.0	47.5	48.0
Litter incidence (´n`)
Number ofin uterofoetal death: early -                     0 -                     1 -                     2 -                     3	13 7 2 1	12 6 3	13 6 4 1	10 8 3 1
Number ofin uterofoetal death: late: -                     0 -                     1 -                     2	19 4	21	21 3	19 2 1
Number ofin uterofoetaldeath: early and late: -                     0 -                     1 -                     2 -                     3 -                     4	10 10 2   1	12 6 3	11 8 4   1	9 7 4 2

 

Table A6.8.1/05-5:    Foetal abnormalities - prevalence and distribution in litters

Category	No. of affected foetuses/litter (n)	Group (Dosage [mg NaBr/kg/day])
		1 (0)	2 (100)	3 (300)	4 (1000)
		No. of litters with ´n` foetuses affected
No. of litters examined		23	21	24	22
Malformation	0	20	21	20	14
	1	2	-	3	5
	2	-	-	1	2
	3	1	-	-	-
	7	-	-	-	1
Visceral anomaly	0	11	10	16	14
	1	11	6	7	3
	2	1	4	1	3
	3	-	1	-	1
	4	-	-	-	1
Skeletal anomaly	0	12	12	6*	4**
	1	6	4	4	3
	2	2	3	6	5
	3	1	2	6	3
	4	2	-	1	5
	5	-	-	1	-
	6	-	-	-	2
Mean foetuses affected per litter [%]
Malformations		1.7	0.0	1.7	5.3
Visceral anomalies		7.8	11.4	5.7	13.2
Skeletal anomalies		13.9	11.9	29.1	40.6

*   statistically different from control with p ≤ 0.05

** statistically different from control with p ≤ 0.01

 

Table A6.8.1/05-6:    Skeletal Variants of Foetuses - Group values

Group (Dosage [mg NaBr/kg/day])	Foetuses examined	Foetuses with
		13 ribs		14 ribs		Normal sternebrae		Unossified sternebrae		Reduced sternebrae		Asym./bip. sternebrae		Total variant sternebrae
		No.	%	No.	%	No.	%	No.	%	No.	%	No.	%	No.	%
1 (0)	159	146	92.5	13	7.5	94	58.6	45	27.9	26	17.9	1	0.4	65	41.4
2 (100)	149	130	88.1	19	11.9	78	51.9	40	27.1	38	25.9	5	3.7	71	48.1
3 (300)	154	153	99.4	1	0.6	64	42.9	62	40.0	37	23.0	5	3.0	90	57.1
4 (1000)	137	137	100.0*	0	0*	27	20.3**	89	63.3**	51	38.8**	5	2.8	110	79.7**

*   statistically different from control with p ≤ 0.05

** statistically different from control with p ≤ 0.01

Applicant's summary and conclusion

Conclusions:

Treatment of pregnant rats with sodium bromide through organogenesis caused severe maternal toxicity at the high dose level of 1000 mg/kg bw/day while at the mid dose level of 300 mg/kg bw/day, maternal toxicity was less pronounced as in the high dose group and was characterised by significantly depressed body weight gains. Taking into consideration the results of the fetal examinations it is concluded that sodium bromide treatment with concentrations of 1000 mg/kg bw/day leads to a higher incidence of foetuses/litters showing absent left kidney, absent left ureter and absent/narrow left uterine horn. Foetuses treated at 300 and 1000 mg/kg bw/day showed a higher incidence of reduced ossification of diverse components of the skeleton. There was no observable maternal or foetal effect related to treatment at 100 mg/kg bw/day while at the mid and high dose level, maternal toxicity as a consequence of treatment with sodium bromide was evident. Therefore, the no effect level for the parent female and in utero development of the foetus is determined to be 100 mg/kg bw/day.

Executive summary:

Materials and Methods

The potential developmental toxicity of sodium bromide was investigated in pregnant Crl: CD BR rats. Dosages of 0, 100, 300 and 1000 mg/kg bw/day were administered daily at a constant volume of 10 mL/kg bw in water as the vehicle by intragastric intubation, to groups of 25 rats each from Days 6-15 post coitum inclusive. On Day 20 post coitum, females were sacrificed and subjected to examination, litter values determined and foetuses subsequently sexed. Half of the foetuses were examined for visceral abnormalities; the remainder were observed for skeletal changes. During the study, clinical signs, body weights, body weight gains and food consumption of dams were regularly examined and reproduction parameters were determined after Cesarian section.

Results and Discussion

Treatment of pregnant dams with sodium bromide during gestation days 6 through 15 was associated with clear signs of maternal toxicity principally manifest as a lower rate of bodyweight gain during Days 6-12 of pregnancy, abnormalities of gait, reduced bodytone and poorly coordinated movements at the top dose level of 1000 mg/kg bw/day. No effects on the reproductive performance, fetal deaths, fetal weight as well as on the sex ratio was evident on comparison of treated groups with concurrent controls. Detailed examination of foetal morphology at this dose level revealed a higher incidence of foetuses/litters showing absent left kidney, absent left ureter, absent/narrow left uterine horn, distorted ribs, shortening/absence of 13th ribs, irregular ossification of the thoracic vertebral centra, reduced and/or unossified sternebrae and, reduced ossification of one or more cranial centres, than in the control group. Although it was noted that seven foetuses in one litter had no left kidney and ureter (3 of these foetuses also had an absent or narrow left uterine horn), these abnormalities were also apparent for one foetus in each of two further litters. In addition, one foetus in another litter had a small left kidney, absent left ureter and a markedly narrow left uterine horn. Therefore, an association with treatment of dams is considered likely, since the litter and not the foetus is the principal unit of assessment, but these effects are probably secondary to severe maternal toxicity at this dose level. It is noteworthy that there was no obvious reduction in mean foetal weight. Some of the observed skeletal abnormalities may reflect effects on maternal bodyweight gain and food consumption. In contrast, the defects observed in the urogenital system are extremely rare and considered more likely to reflect a selective effect on embryofoetal development than a secondary effect resulting from toxicity to the parent female. At 300 mg/kg bw/day, no adverse effects on the parent female were observed during the treatment period. However, following the withdrawal of treatment, bodyweight gain was statistically significantly lower than controls. This effect was also recorded at 1000 mg/kg bw/day on the present study. This is circumstantial evidence that the lower rate of bodyweight gain following the withdrawal of treatment reflects an earlier effect during the dosing period, which has been detected within the context of this screening study. Detailed examination of foetal morphology revealed a higher incidence of foetuses showing reduced ossification of various components of the skeleton compared with controls. It is noteworthy that there was no obvious reduction in mean foetal weight. At 100 mg/kg bw/day, there was no observeable maternal response to treatment and no obvious adverse effects on morphological development of the conceptus.