A fifty-two-week repeated dose toxicity test of 2-(2'-hydroxy-3',5'-di-tert-butylphenyl) benzotriazole was carried out in male and female rats with oral administration at 0, 0.1, 0.5 and 2.5 mg/kg for the males and at 0, 0.5, 2.5 and 12.5 mg/kg for the females. Ten animals each in all group were used for necropsy at the end of the 13- and 52-week administration periods.

There were no deaths related to administration of the test article.

The males of the 2.5 mg/kg group showed low body weights and high food consumption during the administration period.

On urinalysis, the males of the 2.5 mg/kg group exhibited high values for osmotic pressure and/or specific gravity at weeks 13 and 52. At week 52, high values for osmotic pressure and specific gravity were also observed in males of the 0.5 mg/kg group, and high urine volume and low osmotic pressure in females given 12.5 mg/kg.

On hematological examination, high platelet and low erythrocyte values were observed in males of the 2.5 mg/kg group, and low values for hematocrit and/or hemoglobin in males of the 0.5 and 2.5 mg/kg groups, at weeks 13 and 52. At week 52, high platelet values were observed in females of the 12.5 mg/kg group, and prolongation for the PT and APTT in males of the 2.5 mg/kg group.

On blood chemical examination, males of the 0.5 and 2.5 mg/kg groups showed high values for A/G and albumin ratios, ALP, glucose and/or BUN and low values for a1-, a2- and/or b-globulin ratios at weeks 13 and 52. Females of the 12.5 mg/kg group also showed high values for A/G and albumin ratios and/or ALP and low values for a2- and/or b-globulin ratios. At week 52, males of the 0.5 mg/kg group also exhibited high A/G ratios, and females of the 12.5 mg/kg group showed high values for glucose and BUN and low a1-globulin ratios.

At necropsy, enlargement of the liver was observed in males of the 2.5 mg/kg group and in females of the 12.5 mg/kg group at weeks 13 and 52. At week 52, enlargement of the liver was observed in males of the 0.5 mg/kg group, and light gray macules in livers of males in the 2.5 mg/kg group and one female of the 12.5 mg/kg group.

On organ weight measurement, high values for absolute and relative liver weights were observed for males of the 0.5 and 2.5 mg/kg groups and for females of the 12.5 mg/kg group, along with high values for relative kidney weights in males of the 2.5 mg/kg group at weeks 13 and 52.

On histopathological examination, centrilobular hypertrophy of hepatocytes was observed mildly or moderately in males of the 0.5 and 2.5 mg/kg groups and in females of the 12.5 mg/kg group at weeks 13 and 52. At week 52, the incidence of focal necrosis of hepatocytes also tended to be increased in males of the 2.5 mg/kg group in comparison with the controls.

From the above, the NOAELs are considered to be 0.1 mg/kg/day for males and 2.5 mg/kg/day for females.

SUMMARIZED DATA FROM THE STUDY

1. Repeated Dose Oral Toxicity 1)

Purity	:	100 %
Test species/strain	:	Rat/Crj:CD(SD)IGS
Test method	:	Chronic Oral Toxicity Study
Route	:	Oral(gavage)
Dosage	:	0(vehicle), 0.1, 0.5, 2.5 mg/kg/day for males 0(vehicle), 0.5, 2.5, 12.5 mg/kg/day for females
Number of animals/group	:	Males, 20; females, 20
Vehicle	:	Corn oil
Administration period	:	Males and females, 52 weeks
Terminal killing	:	Males and females, 13 or 52 weeks
GLP	:	Yes

　Test Results:

There were no deaths or abnormal clinical signs related to administration of the test article.

On body weight measurement, a low value was observed in the males of the 2.5 mg/kg group on and after day 36.

A high value was observed for food consumption, in males of the 2.5 mg/kg group on and after day 120.

On urinalysis, high values for osmotic pressure and specific gravity were observed in males of the 2.5 mg/kg group at week 13. In week 52, high values for osmotic pressure were also observed in males of the 0.5 and 2.5 mg/kg groups, and for specific gravity in males of the 0.5 mg/kg group. Females of the 12.5 mg/kg group demonstrated high urine volume and low osmotic pressure.

On hematological examination, high platelet and low erythrocyte counts were observed in males of the 2.5 mg/kg group, and low values for hematocrit and hemoglobin in males of the 0.5 and 2.5 mg/kg groups at week 13. At week 52, high platelet counts were observed in males of the 2.5 mg/kg group and females of the 12.5 mg/kg group, and lowering or a tendency toward to lower values for erythrocytes and hematocrit in males of the 0.5 and 2.5 mg/kg groups. PT and APTT were prolonged or tended to be prolonged in males of the 2.5 mg/kg group.

On blood chemical examination, high or tendencies toward elevated values for A/G and albumin ratios and ALP and lowered values for a2- and b-globulin ratios were observed in males of the 0.5 and 2.5 mg/kg groups and in females of the 12.5 mg/kg group at week 13. Males of the 0.5 and 2.5 mg/kg groups also showed high values for glucose and BUN and low values for the a1-globulin ratio, and females of the 12.5 mg/kg group showed high values for total protein. In week 52, high or tendencies toward elevated values for A/G ratio and ALP and lowered or tendencies for lowered values for a1- and a2-globulin ratios were observed in males of the 0.5 and 2.5 mg/kg groups and females of the 12.5 mg/kg group. High values for the albumin ratio were also observed in males of the 0.5 and 2.5 mg/kg groups, elevated BUN and low b-globulin ratios in males of the 2.5 mg/kg group, and high glucose values in females of the 12.5 mg/kg group.

On necropsy, enlargement of the liver was observed in 5 males of the 2.5 mg/kg group and in one female of the 12.5 mg/kg group at week 13. At week 52, enlargement of the liver was observed in 7 and 9 males in the 0.5 and 2.5 mg/kg groups, respectively, and in 5 females in the 12.5 mg/kg group. Light gray macules in the liver were also observed in 2 males of the 2.5 mg/kg group and in one female of the 12.5 mg/kg group.

On organ weight measurement, elevated absolute and relative liver weights were observed in males of the 0.5 and 2.5 mg/kg groups and in females of the 12.5 mg/kg group, and high values for relative kidney weights in males of the 2.5 mg/kg group at weeks 13 and 52.

On histopathological examination, centrilobular hypertrophy of hepatocytes in the livers was observed mildly or moderately in 3 and 9 males of the 0.5 and 2.5 mg/kg groups, respectively, and in 6 females of the 12.5 mg/kg group at week 13. At week 52, centrilobular hepatocyte hypertrophy was again observed mildly or moderately in 5 and 8 males of the 0.5 and 2.5 mg/kg groups, respectively, and in 4 females of the 12.5 mg/kg group. The incidence of focal necrosis of hepatocytes also tended to be increased in males of the 2.5 mg/kg group in comparison with the controls.

From above results, the NOAELs are considered to be 0.1 mg/kg/day for males and 2.5 mg/kg/day for females.