ABSTRACT

On hematological examination, the prothrombin time was significantly shortened in females given 20 mg/kg or more, while the activated partial thromboplastin time was prolonged in both sexes given 500 mg/kg. On histopathological examination, hyaline droplet and eosinophilic body depositions and epithelial regeneration were observed in the renal tubules of males given 20 mg/kg or more. The change in female kidneys at 100 mg/kg was characterized by dilated glomerular capillaries. The test compound also exerted some effects on the liver, adrenal glands and small intestine of both sexes given 100 and/or 500 mg/kg, with blood chemical changes which were indicative of hepatic dysfunction, an increase in liver weights, hepatocellular swelling, vacuolation of adrenocortical cells and epithelial vacuolation of the intestinal mucosa. The NOEL for repeat dose toxicity is considered to be 4 mg/kg/day for both sexes.

1,4-Dibromobenzene was not mutagenic in Salmonella typhimurium TA100, TA98, TA1535, TA1537 and Escherichia coli WP2 uvrA. In the presence of an exogenous metabolic activation system, this chemical substance induced structural chromosomal aberrations in CHL/IU cells. Polyploid cells were not induced under the experimental conditions.

SUMMARIZED DATA OF THE STUDIES

1. Repeat Dose Toxicity 1)

Purity	:	99.9%
Test species/strain	:	Rat/Crj:CD (SD)
Test method	:	Guideline for 28-Day Repeat Dose Toxicity Testing of Chemicals (Japan)
Route	:	Oral (gavage)
Dosage	:	0 (vehicle), 4, 20, 100 and 500mg/kg/day
Number of animals	:	Male, 6; female, 6/group
Vehicle	:	Sesame oil
Administration period	:	Male and female, 28 days
Terminal kill	:	Male and female, days 29 or 43
GLP	:	Yes

　Test results:

Food consumption decreased in both sexes during the early stage of administration and one male died in the 500mg/kg group. However, there were no compound-related changes in body weights and general conditions in either sex. On hematological examination, the prothrombin time was significantly shortened in females receiving 20mg/kg or more, while the activated partial thromboplastin time was prolonged in both sexes given 500mg/kg. On blood chemical examination, increases in total cholesterol, total bilirubin and chloride as well as a decrease in glucose were observed in males and/or females receiving 100mg/kg or more. Additionally, there were increases in GPT, γ-GTP, total protein and triglyceride in both sexes, urea nitrogen and inorganic phosphorus in males, and calcium in females that received 500mg/kg. Increases in weights of the liver and kidneys were also detected in males receiving 100mg/kg and in both sexes receiving 500mg/kg. On histopathological examination, hyaline droplet and eosinophilic body deposition and epithelial regeneration were observed in the renal tubules of males receiving 20mg/kg or more. The change in female kidneys at 500mg/kg was characterized by dilated glomerular capillaries. Hepatocytes were swollen and adrenocortical cells were vacuolated in both sexes receiving 100mg/kg or more. The 500mg/kg males and females showed a whitish appearance of the small intestine as a necropsy finding, and fat deposition in mucosal epithelia as a histopathological finding.

The NOEL for repeat dose toxicity is considered to be 4 mg/kg/day for both sexes.

2. Genetic Toxicity

2-1 Bacterial test 2)

Purity	:	99.9%
Test species/strains	:	S.typhimurium TA100, TA1535, TA98, TA1537 E. coli WP2 uvrA
Test method	:	Guidelines for Screening Mutagenicity Testing of Chemicals (Japan)
Procedures	:	Plate incorporation method
Solvent	:	Acetone
Positive controls	:	-S9, AF-2 (TA100, WP2, TA98), sodium azide (TA1535) and 9-aminoacridine (TA1537) +S9, 2-aminoanthracene (all strains)
Dosage	:	without metabolic activation 0, 6.3, 12.5, 25, 50, 100, 200, 400 μg/plate (TA1535, TA98, WP2, TA1357), 0, 1.6, 3.1, 6.3, 12.5, 25, 50, 100, 200, 400 μg/plate (TA100) metabolic activation method 0, 12.5, 25, 50, 100, 200, 400, 800 μg/plate (TA1535, TA98, WP2, TA1357), 0, 1.6, 3.1, 6.3, 12.5, 25, 50, 100, 200, 400, 800 μg/plate (TA100)
S-9	:	Rat liver, induced with phenobarbital and 5,6-benzoflavone
Plates/test	:	3
Number of replicates	:	2
GLP	:	Yes

　Test results:

Minimum concentration of test substance at which toxicity was observed:

Toxicity was observed at a concentration of 100μg/plate without metabolic activation and 200μg/plate with metabolic activation.

Genetic effects:
S. typhimurium TA100, TA1535, TA 98, TA1537

	+	?	-
with metabolic activation:	[ ]	[ ]	[*]
without metabolic activation:	[ ]	[ ]	[*]

E. coli WP2 uvrA

with metabolic activation:	[ ]	[ ]	[*]
without metabolic activation:	[ ]	[ ]	[*]

2-2. Non-bacterial in vitro test (chromosomal aberration test) 2)

Purity	:	99.9%
Type of cell used	:	Chinese hamster CHL/IU cells
Test method	:	Guidelines for Screening Mutagenicity Testing of Chemicals (Japan)
Solvent	:	0.5% Carboxymethyl cellulose sodium
Positive controls	:	-S9, Mitomycin C +S9, Cyclophosphamide
Dosage	:	-S9 (continuous treatment): 0, 0.3, 0.6, 1.2 mg/ml -S9 (short-term treatment): 0, 0.6, 1.1, 2.2 mg/ml +S9 (short-term treatment): 0, 0.6, 1.1, 2.2 mg/ml
S-9	:	Rat liver, induced with phenobarbital and 5,6-benzoflavone
Plates/test	:	2
GLP	:	Yes

　Test results:

In all short-term treatment groups with S9 mix, more than 10% of cells were observed to have structural aberrations (including gaps).

Lowest concentration producing cytogenetic effects in vitro:

without metabolic activation (continuous treatment ): > 1.2 mg/ml

without metabolic activation (short-term treatment): > 2.2 mg/ml

with metabolic activation (short-term treatment): 0.6 mg/ml (clastogenicity)

Genotoxic effects:

	clastogenicity			polyploidy
	+	?	-	+	?	-
without metabolic activation:	[ ]	[ ]	[*]	[ ]	[ ]	[*]
with metabolic activation:	[*]	[ ]	[ ]	[ ]	[ ]	[*]

1)	The tests were performed by the Research Institute for Animal Science in Biochemistry and Toxicology, 3-7-11 Hashimotodai, Sagamihara-shi, Kanagawa 229, Japan. Tel 81-427-62-2775 Fax 81-427-62-7979
2)	The tests were performed by the Hatano Research Institute, Food and Drug Safety Center, 729-5 Ochiai, Hadano-shi, Kanagawa 257, Japan. Tel +81-463-82-4751 Fax +81-463-82-9627