Potassium bromide

Toxicity to reproduction

Administrative data

Endpoint:

multi-generation reproductive toxicity

Remarks:

based on test type (migrated information)

Type of information:

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

Adequacy of study:

key study

Study period:

1983

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No food consumption, pup body weights and pup litter sizes determined.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

Toxicity of Sodium Bromide in Rats – Effects on endocrine system and Reproduction

Author:

Van Leeuwen, F. X. R. et al

Year:

1983

Bibliographic source:

Fil. Che. Toxic; Vol 21, No. 4, 383-399

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)

Version / remarks:

and study was performed according to good experimental practice

Deviations:

yes

Remarks:

No food consumption, pup body weights and litter size determination

GLP compliance:

no

Remarks:

GLP was not obligatory at the time of study conduct and study was performed according to good experimental practice

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
- Analytical purity: not examined
- Lot/batch No.: not applicable
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:

not specified

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Not applicable
- Age at study initiation: Male rats were mated for the first time at the age of 4 months
- Weight at study initiation: no data

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: No vehicle used; test substance was applied via food

Details on exposure:

Dosing regime followed that of van Logten et al (1974) 90-day repeat oral dose study: NaBr Section 8.6.2 - subchronic repeat dose Van Logten et al (1974) Supp

Details on mating procedure:

Male rats of proven fertility were mated with females for the first time at the age of 4 months. In three successive generations, at least two litters per female rat were raised. In the first generation a third litter was raised for the investigation of transplacental transport of bromide. Furthermore, an additional litter was bred with parent animals of the highest dose group which were changed to the control diet in order to investigate the reversibility of observed effects.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

Not indicated

Frequency of treatment:

Not indicated

Details on study schedule:

No additional details on study schedule given.

Doses / concentrations

Remarks:

Doses / Concentrations:
75, 300, 1200, 4800 and 19200 mg NaBr/kg diet
Basis:
nominal in diet
(corresponding to 5.6, 22.5, 90, 360 and 1400 mg/kg bw/day with 1ppm=0.075 mg/kg bw/day)

No. of animals per sex per dose:

7-19 animals/sex/group

Control animals:

yes, plain diet

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: animals were observed for adverse clinical signs during the treatment period


BODY WEIGHT: Yes
- Time schedule for examinations: at start and termination of the study


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
not examined

Oestrous cyclicity (parental animals):

No data

Sperm parameters (parental animals):

No data

Litter observations:

PARAMETERS EXAMINED
fertility, viability, body weight


GROSS EXAMINATION OF DEAD PUPS:
organ weights were determined for adrenals, thyroid, pituitary, testes, prostate, ovaries and uterus
PARAMETERS EXAMINED
fertility, viability, body weight

Postmortem examinations (parental animals):

GROSS NECROPSY
no data

Postmortem examinations (offspring):

HISTOPATHOLOGY / ORGAN WEIGTHS
organ weights were determined for adrenals, thyroid, pituitary, testes, prostate, ovaries and uterus.

Statistics:

No data

Reproductive indices:

Fertility Index = no. of pregnancies x 100/no. of matings

Offspring viability indices:

Viability Index = no. of pups alive at Day 5 x 100/no. of pups born alive.
Lactation Index = no. of pups alive at Day 21 x 100/no. of pups alive at Day 5

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

effects observed, treatment-related

Body weight and weight changes:

not examined

Food consumption and compound intake (if feeding study):

not examined

Organ weight findings including organ / body weight ratios:

not examined

Histopathological findings: non-neoplastic:

not examined

Other effects:

not examined

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

effects observed, treatment-related

Reproductive function: sperm measures:

effects observed, treatment-related

Reproductive performance:

not specified

Details on results (P0)

CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS)
F0 animals: A dose-dependent decrease in thyroxine (T4) concentration was observed in the serum. Sodium bromide concentrations in the range of 125-2000 mg/kg diet in combination with ´chloride-free` diet in addition revealed decreased thyroxine concentrations in serum in animals treated at 500 and 2000 mg/kg. Uptake of radiolabelled iodide was measured within this experiment and showed significatly increased uptake after 500, but only slight increase after 125 and 2000 mg NaBr/kg diet.
F1 parents: No effects were described in the investigation.

REPRODUCTIVE FUNCTION: ESTROUS CYCLE (PARENTAL ANIMALS)/REPRODUCTIVE FUNCTION: SPERM MEASURES (PARENTAL ANIMALS)/REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
Animals treated at 19200 mg/kg diet were not fertile, and fertility of the next lower dose level (4800 mg/kg diet) was reduced. Because of the diminished fertility in these dosage groups, second and third generations were bred only from the groups dosed with sodium bromide concentrations up to 1200 mg/kg diet. In these groups no effects related to treatment were found in the breeding results.
To investigate whether infertility occurred in males or in females, untreated males and females were mated with females and males of the highest dosage group. Of the treated females with untreated males only 20% became pregnant, and none of the untreated females mated with treated males became pregnant.
Reversibility of the observed effects were studied in animals fed a diet containing 19200 mg NaBr/kg for 7 month followed by a control diet for 3 months before mating. In contrast to the infertility of these animals observed before, fertility index was 62%, viability index 61% and lactation index 90%.

OTHER FINDINGS (PARENTAL ANIMALS)
The lactation index was comparable among all groups investigated.

Effect levels (P0)

1

Dose descriptor:

NOAEL

Remarks:

Systemic

Effect level:

300 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: NOAEL for systemic toxicity: 300 mg NaBr/kg diet, corresponding to 30 mg/kg bw/day NaBr (23.3 mg/kg bw/day “bromide”) and 15 mg /kg bw/day NaBr (11.7 mg/kg bw/day “bromide”) for young and older rats, respectively

2

Dose descriptor:

NOAEL

Remarks:

Reproductive

Effect level:

1 200 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: NOAEL for reproductive toxicity: 1200 mg NaBr/kg diet, corresponding to 120 mg/kg bw/day NaBr (93.2 mg/kg bw/day “bromide”) and 60 mg /kg bw/day NaBr (46.6 mg/kg bw/day “bromide”) for young and older rats, respectively.

Remarks on result:

other: Generation: P and F1 (migrated information)

3

Dose descriptor:

NOAEL

Remarks:

developmental

Effect level:

1 200 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: NOAEL for developmental toxicity: 1200 mg NaBr/kg diet, corresponding to 120 mg/kg bw/day NaBr (93.2 mg/kg bw/day “bromide”) and 60 mg /kg bw/day NaBr (46.6 mg/kg bw/day “bromide”) for young and older rats, respectively

Remarks on result:

other: Generation: F1 and F2 (migrated information)

4

Dose descriptor:

LOAEL

Remarks:

Systemic

Effect level:

1 200 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Remarks on result:

other: Generation: P and F1 (migrated information)

5

Dose descriptor:

LOAEL

Remarks:

Reproductive

Effect level:

4 800 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Remarks on result:

other: Generation: P and F1 (migrated information)

6

Dose descriptor:

LOAEL

Remarks:

Development

Effect level:

4 800 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Remarks on result:

other: Generation: F1 and F2 (migrated information)

Results: F1 generation

General toxicity (F1)

Clinical signs:

not examined

Mortality / viability:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Sexual maturation:

not specified

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

not examined

Histopathological findings:

not examined

Details on results (F1)

VIABILITY (OFFSPRING)
Pup viability at the 4800 ppm dose levels was significantly reduced but survival was shown to be greater in the second when compared to the first litter. All the young of the first litter alive on post-natal day 5 died before day 21 while all young alive on post-natal day 5 were still alive on day 21 in the second litter. No effects on breeding were observed at dose levels of 1200 ppm and below

BODY/ORGAN WEIGHTS (OFFSPRING)
Body- and organ-weight determination did not reveal a clear pattern of dose-related effects in neither of the three generations. Only the adrenals of females of the F0 generation showed a dose-dependent decrease in relative weight which could not be observed in later generations.

Overall reproductive toxicity

Reproductive effects observed:

not specified

Any other information on results incl. tables

Litter observations:

Breeding results with fertility index, viability index and lactation index are given in table 6.8.2/02-1. No data for the dose groups on litter size and sex ratio are given.

Pup mean bodyweights on Day 21 did not differ between control and treatment groups (see table 6.8.1/02-1).

Viability of the young was greater in the second litter than in the first. Furthermore, during the lactation of the first litter all of the young alive at Day 5 died before Day 21. In the second litter, all animals alive at Day 5 were still alive at Day 21.

Macroscopic examination of all pups born during the entire experimental period provided no evidence of anomalies.

Table 6.8.2/02-1:Breeding results in reproduction study on sodium bromide - fertility index, vability index, lactation index and mean bodyweight

Generation	Values for groups fed NaBr at dietary levels [mg/kg diet]
	0	75	300	1200	4800	19200
	Fertility index*
F0	70	70	72	65	25	0
F1	62	54	44	53	-	-
F2	52	67	30	45	-	-
	Viability index**
F0	90	98	96	92	32/61^¥	-
F1	92	88	80	97	-	-
F2	96	98	93	98	-	-
	Lactation index***
F0	95	96	95	94	0/100^¥	-
F1	93	85	72	80	-	-
F2	99	99	99	99	-	-
	Mean bodyweight at Day 21
F0	40	45	43	43	-/38^¥	-
F1	41	43	40	38	-	-
F2	36	38	38	36	-	-

*             Fertility index: No. of pregnancies x 100/No. of matings

**           Viability index: No. of pups alive at Day 5 x 100/No. of pups born alive

***         Lactation index: No. of pups alive at Day 21 x 100/No. of pups alive at Day 5

^¥                     data are given separately for first and second litter

Table 6.8.2/02-2:Bromide concentration in plasma, placenta and kidneys of dams fed 75-4800 mg NaBr/kg diet for 7 months and in foetal kidneys

Dietary concentration of NaBr [mg/kg]	Maternal bromide levels			Bromide level in foetal kidneys [mmol/kg]
	Plasma [mmol/L]	Placenta [mmol/kg]	Kidney [mmol/kg]
75	0.5 ± 0.1	0.4 ± 0.1	0.3 ± 0.1	0.3 ± 0.1
300	2.2 ± 0.1	1.4 ± 0.1	1.4 ± 0.3	0.9 ± 0.1
1200	7.8 ± 0.9	6.3 ± 1.5	4.4 ± 1.1	3.2 ± 0.8
4800	27.6 ± 2.8	16.7 ± 1.5	15.3 ± 1.4	11.0 ± 0.6

Values are means ± SD for groups of seven animals

Table 6.8.2/02-3:Bodyweights and relative organ weights

Generation	Parameter	Values for groups fed NaBr at dietary levels [mg/kg]
		0	75	300	1200	4800
MALES
F0	No./group	9	9	9	10	10
	Bodyweight	422	398	381	391	362
	Adrenals	0.011	0.011	0.011	0.011	0.012
	Thyroid	0.0060	0.0057	0.0056	0.006	0.006
	Pituitary	0.0029	0.0029	0.0029	0.003	0.0033
	Testes	9.68	0.745	0.776**	0.744	0.712
	Prostate	0.119	0.13	0.121	0.135	0.134
F1	No./group	10	10	10	10	-
	Bodyweight	409	391	388	395	-
	Adrenals	0.01	0.01	0.011	0.012	-
	Thyroid	0.0063	0.0064	0.006	0.0067	-
	Pituitary	0.0026	0.0026	0.0027	0.0028	-
	Testes	0.771	0.759	0.769	0.763	-
	Prostate	0.077	0.093	0.093	0.102*	-
F2	No./group	10	10	10	10	-
	Bodyweight	438	373**	397*	378**	--
	Adrenals	0.01	0.01	0.009	0.01	-
	Thyroid	0.0076	0.0074	0.007	0.0081	-
	Pituitary	0.0032	0.0031	0.0027**	0.0029	-
	Testes	0.787	0.821	0.679	0.793	-
	Prostate	0.103	0.12	0.109	0.104	-
FEMALES
F0	No./group	7	11	9	12	11
	Bodyweight	254	256	249	243	249
	Adrenals	0.02	0.019	0.019	0.017*	0.017**
	Thyroid	0.0062	0.0066	0.0066	0.0073	0.0073
	Pituitary	0.0056	0.0055	0.0052	0.0052	0.0046*
	Ovaries	0.022	0.021	0.022	0.025	.024
	Uterus	0.171	0.166	0.18	0.15	0.143
F1	No./group	19	15	14	16	-
	Bodyweight	244	254	252	241	-
	Adrenals	0.018	0.018	0.017	0.017	-
	Thyroid	0.0073	0.007	0.0074	0.0083	-
	Pituitary	0.0047	0.0052	0.0049	0.0053*	-
	Ovaries	0.026	0.029	0.027	0.027	-
	Uterus	0.167	0.159	0.15	0.14*	-
F2	No./group	10	10	10	10	-
	Bodyweight	267	244	259	241**	-
	Adrenals	0.019	0.018	0.017	0.018	-
	Thyroid	0.0096	0.0083	0.0094	0.0103	-
	Pituitary	0.0053	0.0048	0.005	0.0056	-
	Ovaries	0.027	0.024	0.027	0.027	-
	Uterus	0.188	0.16	0.179	0.164	-

Bodyweights are expressed in g.

Organ weights are expressed as g/100 g bodyweight.

*             Significantly different from the control with 0.01≤ P < 005

**           Significantly different from the control with 0.001≤ P < 0.01

 

Applicant's summary and conclusion

Conclusions:

In this three-generation reproductive toxicity study it was demonstrated that administration of 4800 and 19200 ppm of NaBr caused a reduction in the fertility of both sexes of rats, an increased litter loss and pup mortality. A cross-mating experiment revealed that the effects of bromide on reproduction system are reversible as could be shown by one group of animals of the highest dosage level which were changed to control diet and mated again.

Executive summary:

Materials and Methods

The investigations addressed results from bromide studies present in the literature and provided additional data about the effects of bromide in the endocrine and reproductive systems. Estimation of an ADI is discussed in relation to the present residue situation. A three-generation reproduction study in rats was performed using sodium bromide concentrations within a range of 75-19200 mg/kg diet, examining the effects on reproductive system. In three successive generations, at least two litters per female rat were raised. In the first generation, a third litter was raised for the investigation of transplacental transport of bromide. Furthermore, an additional litter was bred with parent animals of the highest dosage group which were changed to control diet in order to investigate reversibility of effects.

Results and Discussion

Formerly performed studies demonstrated that administration of sodium bromide for four weeks at dietary concentrations in the range of 300-19200 mg/kg diet showed that bromide was readily absorbed and within three weeks bromide concentration in plasma reached plateau level (van Logten et al, 1973; please refer to section 6.4.1/03). Anomalies were observed in the highest dose group only. These rats showed signs of motor incoordination of the hind legs and depressed grooming; organ weight determination revealed increased relative weight of the kidneys. No histopathological changes of organs or differences in food consumption and water intake were observed. This was surprising since with replacement of about 50% of chloride through bromide impair of electrolyte balance was expected. These results were further confirmed by a 90-day experiment with the same dose regimen with the addition of a 75 mg NaBr/kg diet group (van Logten et al, 1974; please refer to section 6.4.1/04). In contrast to the short term experiment the investigation over 90 days showed growth retardation in the highest dosage group and decreased food conversion. In addition, a slight decrease in concentration of lymphocytes and doubling of neutrophilic granulocytes were observed. The most prominent effects were seen on the thyroid and gonads: Relative weight of thyroid was increased and relative prostate weight was decreased with both decreased spermatogenesis and vacuolisation of the zona fasciculata; females showed a decrease in the number of corpora lutea. These effects which strongly suggest an impairment of the endocrine system by bromide, have been confirmed in another 90-day experiment studying the effects of a low-chloride intake on bromide toxicity (van Logten et al, 1976; please refer to section 6.4.1/05). In a previous study it had been shown that elimination of bromide from the circulation was strongly dependent upon chloride intake. Omission of chloride from the diet caused an increase in bromide half-life. Low-chloride diet in combination with bromide intake showed effects on the same target organs as the investigations on bromide performed before. In addition, corticosterone concentration in plasma was determined and revealed a decrease at the two highest dosage levels used. This fits well with the histopathological changes in adrenals indicative of a decreased synthesis of glucocorticosteroids. Since this process is regulated by adrenocorticotropic hormone (ACTH) released by the pituitary, the origin of the observed effect might be a dysfunction of the hypothalamus-pituitary axis. Also other observed morphological changes, like a decrease in corpora lutea and impairment of spermatogenesis, and the observed growth retardation could be attributed to a decrease in pituitary function. The former might be due to a decreased secretion of gonadotropic hormone, the latter to a decreased secretion of somatotropic hormone by the pituitary gland. However, it can not be excluded that bromide has a direct effect on the other organs on the endocrine system. In particular, activation of the thyroid can not be explained by a decreased pituitary function. In the present three-generation reproductive toxicity study it was shown that of the high dosed (19200 mg NaBr/kg diet) females mated with untreated males only 20% became pregnant, and none of the untreated females mated with high dosed males became pregnant. Therefore, the observed effect of reduced and absent fertility in the 4800 and 19200 mg/kg diet groups, respectively, were due to infertility of male as well as female rats. This conclusion is in accordance with the histopathological lesions found in the testes as well as in the ovaries in the 90-day studies. In addition, pup viability at the 4800 ppm dose levels was significantly reduced but survival was shown to be greater in the second when compared to the first litter. All the young of the first litter alive on post-natal day 5 died before day 21 while all young alive on post-natal day 5 were still alive on day 21 in the second litter. No effects on breeding were observed at dose levels of 1200 ppm and below. For the group of animals treated at 19200 mg/kg diet, infertility was observed. After 7 month on the high dose level, the diet was changed to control diet for 3 month and rats were mated again. In contrast to the infertility observed before, animals showed fertility index of 62%, viability index of 61% and lactation index of 90%. From these results it is clear that the effects of bromide on reproduction system are reversible but could not be entirely compensated. No macroscopic anomaly in neither pup was observed throughout the investigation, although it is known that bromide easily crosses the placenta. Dams and F1 rats examined for bromide concentrations in internal organs showed equal amounts of bromide in kidney which provides that rats had been exposed to bromide in utero. Body and organ weight determinations did not reveal a clear dose-related pattern. A dose-dependent decrease in T4 levels in serum of parent animals of the F0 generation was observed. This finding is indicative of an inhibitory action of bromide on the synthesis of thyroid hormones, resulting in a physiological feedback mechanism of increased thyrotropic hormone (TSH) secretion by the pituitary gland causing an increased stimulation of the thyroid. This is in good agreement with the activation of the thyroid found by histological examination in the previous 90-day studies mentioned above. The decrease in thyroid hormones in animals treated at high dose levels was confirmed in an experiment on the time dependency of the effect of bromide on the thyroid. Using standard diets containing 4800 and 19200 mg NaBr/kg, significantly decreased thyroxine concentrations were found in both groups. From this experiment, it appeared that after only three days the thyroxine concentration in serum was significantly decreased and that it remained constant during an experimental period of 12 weeks. Experiments using a ´chloride-free`diet revealed reduced T4 levels in serum in animals treated at 500 and 2000 mg NaBr/kg diet. Using radiolabeled iodide, significantly increased iodide uptake for treatment with 500 mg NaBr, but only slight increase for treatment with 125 and 2000 mg NaBr/kg ´chloride-free`diet was observed. For an activated thyroid increased uptake and release of iodide is expected. However, the effect appeared to be biphasic. At 500 mg/kg the uptake was greater than with 2000 mg/kg, in the latter group the uptake was less and the release measured between 24 and 48 hours seemed to be enhanced. This can probably be explained by two opposite effects of bromide on the thyroid. Bromide, as a halogen, competes with iodide for the uptake in the thyroid gland and can replace iodide in thyroid hormones; thus, the synthesis of T4 might be decreased. This would lead to an enhanced stimulation of the thyroid by the pituitary gland. At 2000 mg/kg diet, the bromide concentration in the serum is probably so high in relation to that of iodide that even an activated thyroid takes up relatively more bromide than iodide. Therefore, in this dose group the iodide uptake by the thyroid might be less than in the 500 mg/kg group, although the release is faster. In this case, however, the additional possibility of a diminished stimulatory action of the pituitary at the highest dose level cannot be excluded. Although bromide has a very low acute oral toxicity, a striking complex of presumably related changes in the endocrine system was observed on subchronic administration. The most prominent alteration appeared to be the effect on the thyroid, found histopathologically and by the measurement of circulating thyroid hormones. Also in the present three-generation toxicity study, the decrease in thyroid hormones was the most sensitive criterion. On the basis of the effect on the thyroid in the 90-day study, a NOAEL of 300 mg/kg diet can be determined in the rat. For bromide ion this value is corresponding to 11.7 mg/kg bw/day for older rats (23.4 mg/kg bw/day for young rats). In an experiment with human volunteers dosed daily with 1 mg/kg bw for 8 weeks no changes in haematological, biochemical or endocrinological parameters were found. Plasma bromide levels determined in the volunteers were about 0.9 mmol/L, approximately 10% of the bromide concentration of 8 mmol/L found to induce alterations in the thyroid of rats. Therapeutic range of bromide is 6-12 mmol/L in man.