DATA EVALUATION RECORD

Tribenuron Methyl (DPX-L5300)

PC Code: 128887

TXR#: 0056213

MRID#: 48732501

Study Type: Acute Neurotoxicity Study in Rats;

OPPTS 870.6200a

Prepared for

Health Effects Division

Office of Pesticide Programs

U.S. Environmental Protection Agency

One Potomac Yard

2777 S. Crystal Drive

Arlington, VA 22202

Prepared by

Tetrahedron Incorporated

1414 Key Highway, Suite B

Baltimore, MD 21230

Principal Reviewer: ______________________________________ Date: 4/23/2012

Ahmed Elnabawi, Ph.D.

Secondary Reviewer: _____________________________________ Date: 4/24/2012

Katherine Squibb, Ph.D.

Quality Assurance: _________________________________________ Date: 4/26/2012

Nasrin Begum, Ph.D.

Contract Number: EP-W-10013

Work Assignment No.: WA-0-01

Task Number: 1-1-87

EPA Reviewer//WAM: Christina Swartz and Alan Levy// Kit Farwell and Lori Brunsman

Disclaimer

This review may have been altered by the EPA subsequent to the contractors’ signature 

above.
Acute Neurotoxicity Study (rats) (2012) /Page 2 of 16

Tribenuron Methyl/128887 OPPTS 870.6200a/ MAFF 12 Nousan 8147/OECD 424

EPA Reviewer: Jaime D’Agostino Signature: 

Risk Assessment Branch 2, Health Effects Division (7509P) Date: 

Work Assignment Manager: Lori Brunsman Signature: 

Science Info. Mgmt. Branch, Health Effects Division (7509P) Date:

Template version 09/11

TXR#: 0056213

DATA EVALUATION RECORD

STUDY TYPE: Acute Neurotoxicity, (oral, gavage) – (rat); OPPTS 870.6200a [§81-8], OECD 

424; MAFF12 Nousan 8147; EEC B.43 Directive 2004/73/EC

PC CODE: 128887 DP BARCODE: D397466; D398740; D398929

TEST MATERIAL (PURITY): Tribenuron Methyl (DPX-L5300) (98.2% a.i.).

SYNONYMS: Methyl 2-[[[[(4-methoxy-6-methyl-l,3,5-triazin-2-yl)methylamino]carbonyl]

amino]sulfonyl]benzoate; Methyl 2-[4-methoxy-6-methyl-l,3,5-triazin-2-

yl(methyl)carbamoylsulfamoyl]benzoate; DPX-L5300-281

CITATION: Carpenter, C. (2012). Tribenuron Methyl (DPX-L5300) Technical: Acute Oral 

Neurotoxicity Study in Rats. E.I. du Pont de Nemours and Company, DuPont 

Haskell Global Centers for Health and Environmental Sciences,, Newark, 

Delaware, U.S.A. Laboratory project numbers: DuPont-31859, January 13, 2012. 

MRID 48732501. Unpublished.

Carpenter, C. (2011). Tribenuron Methyl (DPX-L5300) Technical: Acute Oral 

Neurotoxicity Study in Rats. E.I. du Pont de Nemours and Company, DuPont 

Haskell Global Centers for Health and Environmental Sciences,, Newark, 

Delaware, U.S.A. Laboratory project numbers: DuPont-31859, December 15, 

2011. MRID 48703401. Unpublished.

SPONSOR: E.I. du Pont de Nemours and Company, Wilmington, Delaware 19898, U.S.A.

EXECUTIVE SUMMARY:

In an acute neurotoxicity study (MRID 48703401 and 48732501; revised report), groups of 

Crl:CD(SD) rats (12/sex/dose) were administered a single oral (gavage; 10 ml/kg) dose of 

Tribenuron Methyl (DPX-L5300) (98.2 %) in 0.5% methylcellulose at doses of 0, 100, 300, or 

1000 mg/kg bw and observed for 14 days. Neurobehavioral assessment (functional observational 

battery and motor activity testing) was performed on all animals prior to test substance 

administration (baseline), on Day 0 approximately 2 hours after the treatment, and on Days 7 and 

14. At study termination, 6 animals/sex in the control and high dose groups were euthanized and 

perfused in situ for neuropathological examination. The brain and peripheral nervous system 

tissues collected from the perfused animals in the control and 1,000 mg/kg groups were 

subjected to histopathological evaluation.

There were no treatment-related effects on mortality or clinical signs at any dose level in males 
Acute Neurotoxicity Study (rats) (2012) /Page 3 of 16

Tribenuron Methyl/128887 OPPTS 870.6200a/ MAFF 12 Nousan 8147/OECD 424

and females.

There were no treatment-related effects on mean body weights in the 100, 300 and 1,000 mg/kg 

in males or females, except for a slight, statistically significant, lower body weight (↓7%) in the

1,000 mg/kg group females on Day 7. However, body weight gains were significantly reduced in 

males at 300 and 1000 mg/kg/day and females at 1000 mg/kg/day. 

In males, body weight loss (p≤0.05) was 4.5 g of weight in the 300 mg/kg group and 12.2 g of 

weight in the 1,000 mg/kg group over the interval test Days 0-1 compared to 4.7 g body weight 

gain in the control group. Mean body weight gain was significantly decreased by (↓42%) in the 

1,000 mg/kg females on Day 0-7. No significant differences were noted on overall (Days 0-14) 

body weight gain when compared to the control group in the 1,000 mg/kg males or females. 

Treatment-related effects on food consumption were evident in the 300 and 1,000 mg/kg males 

and females. Food consumption was significantly decreased by ↓25% and ↓65% in the 300 and 

1,000 mg/kg males, respectively, on Day 0-1. Similarly, lower (p≤0.05) food consumption was 

observed at dose level 300 (↓19%) and 1,000 (↓70%) mg/kg in females on Day 0-1. On Day 0-7, 

mean food consumption was significantly (p≤0.05) reduced by ↓10% in the 1,000 mg/kg females 

group, but not in the males. No significant differences were noted on overall (Days 0-14) food 

consumption when compared to the control group in the 1,000 mg/kg males or females. Lower 

(p≤0.05) food efficiency was noted in the 300 mg/kg and 1,000 mg/kg males and the 1,000 

mg/kg females on Day 0-1. In addition, mean food efficiency was significantly (p≤0.05) 

decreased by ↓34% in the 1,000 mg/kg females group on Day 0-7, but not in the males. No 

significant differences were noted on overall (Days 0-14) food consumption in the 1,000 mg/kg 

males or females when compared to the control group.

No treatment-related neurotoxic effects were observed. Transient, significant decreases in motor 

activity (duration of movement) were observed in males (↓44%) and females (↓56%) at the dose 

level of 1,000 mg/kg on Day 0, but not on Days 7 and 14.. Lower (p≤0.05) mean rearing was 

observed in the 1,000 mg/kg females (↓50%) on test Day 0, but not in the males. This finding 

was associated with the reduction in motor activity observed in the 1,000 mg/kg group females 

on Day 0. Significantly (p≤0.05) higher incidences of abnormal sleeping behavior were 

observed in the 1,000 mg/kg group males in the home cage on Day 7. However, it is unclear if 

this is treatment related because it was only observed on Day 7 in males and all other treatment 

related findings were observed on Day 0 or 1. There were no macroscopic and microscopic 

pathology alterations of nervous system tissues in the 1,000 mg/kg male and female groups. The 

transient effects on motor activity and rearing are attributed to the body weight effects, 

significant reductions in food consumption, and/or food efficiency also observed at the same 

dose. 

The LOAEL for systemic toxicity is 1000 mg/kg for males and females, based on body 

weight changes (BW loss in males, decreased BWG in females), reduced food consumption, 

and/or food efficiency, and transient effects on motor activity and rearing, attributed to the

systemic changes observed.

This study is classified as acceptable/guideline and satisfies the guideline requirement (OPPTS 

870.6200a; OECD 424) for an acute neurotoxicity study in rats.

COMPLIANCE: Signed and dated GLP, Quality Assurance, Flagging, and Data Confidentiality

(no claim of confidentiality under FIFRA, but waiver does not apply to other regulatory agencies 

and information is labeled trade secret) were provided. I. MATERIALS AND METHODS:
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A. MATERIALS:

1. Test material: Tribenuron Methyl (DPX-L5300) Technical

Description: White to tan - Solid

Lot/Batch #: MAY10MA047

Purity: 98.2 % a.i.

Compound Stability: The Sponsor stated that the test substance was considered to be stable for 5 days at room 

temperature.

CAS # of TGAI: 101200-48-0

Structure:

2. Vehicle: 0.5% Methylcellulose.

3. Test animals:

Species: Rat

Strain: Crl:CD(SD)

Age/weight at study initiation: 49 days of age. Males: 217.8-293.1 g; Females: 157.9-217.2 g.

Source: Charles River Laboratories International, Inc., Kingston, NY.

Housing: Housed in pairs in solid bottom caging with bedding mixed with enrichment 

(Shepherd’sTM Cob + PLUSTM).

Diet: PMI® Nutrition International, LLC Certified Rodent LabDiet®

5002, ad libitum, 

except during neurobehavioral testing.

Water: Tap water, ad libitum, except during neurobehavioral testing.

Environmental conditions: Temperature:

Humidity:

Air changes:

Photoperiod:

20-26°C

30-70%

Not stated

12 hrs dark / 12 hrs light

Acclimation period: 13 days

B. STUDY DESIGN:

1. In life dates: Start: June 13, 2011; End: June 30, 2011.

2. Animal assignment and dose rational: Animals were randomly assigned to the test groups 

noted in Table 1 using a weight stratification-based computer program. The body weights of 

all animals were within ±20% of the mean weight for each sex. Following assignment to 

groups, rats were subdivided into 4 replicates, each containing an equal representation of 

each group and sex. The replicates were dosed over a 2-day period. Test substance was 

administered once via gavage to rats at dose levels of 0, 100, 300 and 1,000 mg/kg and the 

animals were observed twice daily for 14 days after dosing. Animals were weighed on test 

day 0, 1, 7, and 14. Survivors not assigned for neuropathology were sacrificed and a 

necropsy was not performed.

Dose levels were chosen based on the results of a 28-day oral toxicity study in rats conducted 

with Tribenuron methyl (DPX-L5300) at dose levels of 0, 100, 300, and 1000 mg/kg/day
Acute Neurotoxicity Study (rats) (2012) /Page 5 of 16

Tribenuron Methyl/128887 OPPTS 870.6200a/ MAFF 12 Nousan 8147/OECD 424

(MRID: 42836601) and an acute oral toxicity study in rats conducted with Tribenuron methyl 

Technical at a single dose of 5000 mg/kg body weight (not submitted). 

In the 28-day oral toxicity study, significant lower body weight and body weight gain were 

noted at 300 and 1000 mg/kg/day. In the acute oral toxicity study, body weight losses (10-

13%) were observed at 5000 mg/kg during test days 9-11. No deaths were recorded in this 

study.

Based on these combined results, the dose levels selected for the current study were 0, 100, 

300 and 1,000 mg/kg body weight (Table 1).

TABLE 1. Study Design

Experimental parameter Dose Level (mg/kg bw) 

0 100 300 1,000

Dose formulation concentration (mg/mL) 0 10 30 100

Total number of animals/sex/group 12 12 12 12

Behavioral testing (FOB, Motor activity) 12/sex 12/sex 12/sex 12/sex

Neuropathology (microscopic evaluation) 6/sex 0/sex 0/sex 6/sex

Doses were adjusted for purity and dose volume was 10 mL/kg.

Data were extracted from pages 15 and 18-22 of the study report.

3. Test Substance preparation and analysis: All dose formulations were prepared once prior 

to dosing by mixing appropriate amounts of test substance with 0.5% methylcellulose. They

were stored at room temperature. Homogeneity and concentration analyses of test substance 

in 0.5% methylcellulose were verified prior to the study at concentrations of 0, 10, 30 and 

100 mg/mL. The stability of the test substance was verified at the concentrations of 10 and 

100 mg/mL after 5 days of storage at room temperature.

Results

Homogeneity analysis (% RSD): 1-4%.

Stability analysis (% initial): 94.9-97.7%, 5 days at room temperature.

Concentration analysis (range as % nominal): 96.3-103%. 

These analytical data indicated that the mixing procedure was adequate and that the variance 

between nominal and actual dosage to the animals was acceptable.

4. Statistics: The data were presented as mean ± standard deviation (SD). Each test substance 

exposed group was compared to the control group for the parameters listed below. The data 

were analyzed using the following statistical methods and significance was defined at p<0.05 

for all tests.

Parameters Statistical Methods

- Body weight 

- Body weight gain

Levene’s test for homogeneity and Shaprio-Wilk test for normality. If test was not 

significant, one-way analysis of variance followed by Dunnett’s test (2-sided) was used to 
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-Food consumption

-Food efficiency

compare treated groups with control groups. If test was significant, transforms of the data 

were used. The rank order of transform was log, square-root, and rank-order

- Rearing 

- Grip strength 

- Foot splay

- Body temperature

- Motor activity

Levene’s test for homogeneity and Shaprio-Wilk test for normality. If test was not 

significant, repeated measures analysis of variance was followed by linear contrasts. If test 

was significant, a normalizing, variance stabilizing transformation followed by repeated 

measures analysis of variance or sequential application of the Jonckheere-Terpstra trend test

were used. If there was a significant lack of monotonicity, Dunn’s test was used instead.

FOB, descriptive parameters Cochran-Armitage test for trend; if the incidence was not significant, but a significant lack 

of fit occurred, then Fisher’s Exact test with a Bonferroni-Holm correction was used.

These statistical analyses were considered to be appropriate.

C. METHODS / OBSERVATIONS:

1. Mortality and Clinical Observations: Animals were observed twice daily for mortality and 

morbidity throughout the study. Detailed clinical observations were recorded daily during the 

14 days following dosing except on the days of neurobehavioral evaluations. 

2. Body Weight: Animals were weighed during the baseline FOB, prior to the test substance 

administration, and on Days 1, 7 and 14.

3. Food Consumption: Food consumption of each animal was determined by weighing each 

feeder on test Days 0, 1, 7, and 14. The mean food consumption (g/day) and food efficiency

(average weight gain/average food consumed) were calculated for each rat for the intervals of 

test days 0-1, 0-7, 7-14, and 0-14.

4. Cholinesterase determination: Cholinesterase activity was not evaluated.

5. Neurobehavioral Assessment:

a. Functional Observational Battery (FOB): All animals were subjected to a FOB during

acclimation (baseline) and on Days 0 (approximately 2 hours after dosing), 7 and 14. The 

FOB was conducted by an observer who was “blind” to the treatment status of the 

animal, and the same observer performed all of the evaluations. Animals were acclimated 

for at least 10 minutes prior to evaluation. The FOB evaluations were conducted in a 

sound-attenuated room equipped with a white-noise-generation system to minimize 

variations in environmental test conditions. The time in the open-field was at least 2 

minutes. Fore- and hindlimb grip strength were measured using a Chatillon Digital Force 

gauge. Rectal body temperature was measured with a YSI Precision 4000 thermometer 

and temperature probe.

The following CHECKED (X) parameters were examined.

HOME CAGE OBSERVATIONS REMOVAL FROM THE HOME 

CAGE AND HANDLING

OPEN FIELD OBSERVATIONS

X Posture X Ease of removal X Righting reflex

X Gait/coordination X Ease of handling X Gait/coordination

X Convulsions X Vocalization X Muscle spasms/fasciculation

X Tremors X Muscle tone X Convulsions

X Palpebral closure X Piloerection X Tremors
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NEUROMUSCULAR 

OBSERVATIONS

X Fur/skin appearance X Ease of respiration

X Landing foot splay X Mucous membranes X Rate of respiration 

X Forelimb grip strength X Palpebral closure X Posture

X Hindlimb grip strength X Exophthalmus X Palpebral closure

SENSORY OBSERVATIONS X Lacrimation X Arousal 

X Approach response X Salivation X Vocalization

X Touch response X Dehydration X Diarrhea

X Sharp auditory stimulus X Emaciation X Polyuria

X Tail pinch PHYSIOLOGICAL 

OBSERVATIONS

X Number of rearing movements

X Pupillary constriction X Body temperature

X Body weight

Parameters based on OPPTS Guideline 870.6200.

Data were obtained from pages 20-21 of the study report.

b. Locomotor Activity: Locomotor activity was evaluated after the last animal completed 

the FOB pre-exposure (Day 0) and on Day 7, and Day 14. Animals were 

counterbalanced by sex and treatment and were tested in replicates over multiple days. 

An automated Coulbourn®Instruments activity monitor was used with infrared beams per 

cage for motor activity data collection. The infrared monitoring device enabled 

measurements of two dependent variables: duration of movement and number of 

movements. A continuous movement, regardless of its duration, was counted as one 

movement by the activity measurement system. The technical characteristics of the 

measurement system are such that duration of movement is analogous to “counts” in 

other types of devices that employ interruption of light beams. Duration of movement and 

number of movement were evaluated in 9 consecutive intervals of 10 minutes each as 

well as for the total 90-minute session.

6. Sacrifice and Pathology: 

Animals selected for neuropathological evaluation (6 rats/sexin the control and high dose 

groups) were deeply anaesthetized by i.p. injection of a mixture of ketamine/xylazine and 

perfused in situ. The perfusion and necropsy procedures were conducted according to 

Haskell Standard Operating Procedure-Neurotoxicity Necropsy Procedures. Animals were 

subjected to gross necropsy. The remaining animals were sacrificed using isoflurane 

anesthesia and CO2 and were disposed of without any pathological examinations.

The tissues from the control and high-dose animals (1,000 mg/kg bw) were processed for 

microscopic evaluation. The brain, spinal cord sections, eyes, optic nerve, and gastrocnemius 

muscle were embedded in paraffin, sectioned at 5 μm, and stained with hematoxylin-eosin 

(H&E). The dorsal root ganglia (including dorsal and ventral root fibers) from the cervical 

and lumbar swellings, gasserian ganglia, and peripheral nerves were embedded in 

glycolmethacrylate (GMA), sectioned at 3 μm, and stained with hematoxylin-eosin (H&E). 

Stained histological sections were examined by light microscopy. 

Brain weight and measurements were not evaluated in this study.

The following CHECKED (X) tissues from the control and high-dose animals, as well as all 

gross lesions were evaluated. 
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CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM

BRAIN SCIATIC NERVE

X Olfactory bulb Mid-thigh Region

X Cerebral cortex X Sciatic Nerve

X Hippocampus

X Basal ganglia

X Cerebellum

X Thalamus

X Pons

X Medulla oblongata OTHER

X Midbrain X Tibial nerve

X Hypothalamus X Sural nerve

SPINAL CORD Peroneal Nerve

X Cervical swelling X Lumbar dorsal root ganglion

X Lumbar swelling X Lumbar dorsal root fibers

Thoracic swelling X Lumbar ventral root fibers

OTHER X Cervical dorsal root ganglion

X Gasserian Ganglion X Cervical dorsal root fibers

Trigeminal nerves X Cervical ventral root fibers

X Optic nerve

X Eyes

X Gastrocnemius muscle

7. Positive Controls: It was stated in this report that three separate reports (MRID 44628703, 

MRID 47053501 and MRID 48710304, performed in 1997, 2002 and 2011, respectively)

were previously performed by DuPont Haskell to generate positive control data and validate 

the procedures and the inter-observer reliability of the performing lab to conduct and assess 

neurobehavioral and neuropathology tests. The data also documents that the equipment and 

procedures are capable of detecting effects that may be seen in neurotoxicity studies. The

positive control data is acceptable for use with the current study..

II. RESULTS:

A. OBSERVATIONS:

1. General Clinical Observations: There were no significant treatment-related clinical 

findings in the 100, 300 or 1,000 mg/kg groups of both sexes. The only clinical sign observed 

was a missing toe (hindlimb, left) in one male in the 1,000 mg/kg group from Day 1 to 13. 

2. Mortality: All animals survived to scheduled termination.

B. BODY WEIGHT AND BODY WEIGHT GAIN: There were no treatment-related effects 

on mean body weights in the 100, 300, and 1,000 mg/kg groups in males or females.A slight 

statistically significant lower body weight (↓7%) was noted in the 1,000 mg/kg group 

females on Day 7 (Table 2) but the mild reduction was not considered adverse. Effects on 

body weight gain were observed at 300 and 1000 mg/kg/day. As shown in Table 2, test

substance-treated males lost 4.8 g (↓202%) and 12.2 g (↓359%) of weight (p≤0.05) at dose 

levels of 300 and 1,000 mg/kg, respectively, over the interval test Days 0-1 compared to a 4.7
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g body weight gain in the control group. For females, the only significant (p≤0.05) difference 

from the control group was a lower mean body weight gain (↓42%) in the 1,000 mg/kg group 

between Days 0-7 (Table 2). No significant differences were noted on overall (Days 0-14) 

body weight gain when compared to the control group in the 1,000 mg/kg males or females. 

TABLE 2. Mean (±SD) Body Weights and Body Weight Gains in Male and Female Rats 

Exposure Time Dose (mg/kg)

0 100 300 1,000

Body weight (g) - Males

Day 0 260.5±21.4 259.0±11.7 266.3±12.7 267.4±14.5

Day 1 265.2±23.0 262.3±11.6 261.5±11.7 255.2±13.5

Day 7 321.5±25.4 322.3±18.6 329.9±14.5 323.3±17.5

Day 14 379.7±29.7 378.6±26.0 393.4±16.4 385.2±17.3

Body weight (g) - Females

Day 0 190.0±14.3 188.5±15.5 187.5±11.3 186.2±9.6

Day 1 188.6±13.0 188.0±14.0 185.7±9.6 178.4±10.3

Day 7 214.8±18.5 216.6±20.5 211.4±11.4 200.7±9.0*

(↓7%)

Day 14 237.8±22.7 237.9±24.2 234.0±15.3 226.5±14.7

Body weight gain (g) - Males

Day 0-1 4.7±3.4 3.3±4.6 -4.8±3.8*

(↓202%)

-12.2±7.0*

(↓359%)

Day 0-7 61.0±6.5 63.3±10.0 63.5±6.1 56.0±6.5

Day 7-14 58.2±7.2 56.3±8.8 63.5±7.2 61.9±6.8

Day 0-14 119.2±12.7 119.6±18.2 127.1±8.7 117.9±10.0

Body weight gain (g) - Females

Day 0-1 -1.4±4.6 -0.5±5.9 -1.9±6.9 -7.9±6.5

Day 0-7 24.8±8.0 28.1±7.5 23.9±7.2 14.5±6.6*

(↓42%)

Day 7-14 23.0±7.1 21.3±7.0 22.6±6.7 25.8±10.4

Day 0-14 47.8±9.9 49.4±12.7 46.5±10.5 40.3±11.1

Values represent mean±SD, n=12.

Percent difference from the control is included in parentheses and was calculated by the Reviewers. 

* Significantly different from the control group, p≤0.05.

Data were obtained from pages Tables 3 (page 34), 4 (page (35), 5 (page 36) and 6 (page 37) of the study report.

C. FOOD CONSUMPTION AND FOOD EFFICIENCY: Summary results of food 

consumption and food efficiency in males and females are presented in Table 3. Treatmentrelated effects on food consumption were evident in the 300 and 1,000 mg/kg males and 

females. In males, significant decreases (p≤0.05) in food consumption were noted at dose 

levels of 300 (↓25%) and 1,000 (↓65%) mg/kg on Day 0-1. Similarly, lower (p≤0.05) food 

consumption was observed in females at dose levels of 300 (↓19%) and 1,000 (↓70%) mg/kg 

on Day 0-1. In contrast, food consumption was significantly (p≤0.05) increased by 6% in the 

300 and 1,000 mg/kg male groups on Day 7-14. However, mean food consumption was 

unaffected by the test substance in the females at any dose level on Day 7-14. On Day 0-7, 

mean food consumption was significantly (p≤0.05) reduced by 10% in the 1,000 mg/kg 

females group (Table 3). No significant differences were noted on overall (Days 0-14) food 

consumption in the 1,000 mg/kg males or females when compared to the control group.

Significant (p≤0.05) reductions in food efficiency compared to the control were noted in the 

300 mg/kg and 1,000 mg/kg males and the 1,000 mg/kg females on Day 0-1. In addition, mean 
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food efficiency was significantly (p≤0.05) decreased by ↓34% in the 1,000 mg/kg females 

group on Day 0-7, but not in the males. Food efficiency was decreased in maleson Day 0-1 in 

the 300 and 1,000 mg/kg groups by ↓249% and ↓1,064%, respectively. It is concluded that 

lower food efficiency observed in the 300 mg/kg and 1,000 mg/kg males and the 1,000 females 

on Day 0-1 was consistent with the significant reduction in food consumption observed in the 

300 mg/kg and 1,000 mg/kg males and the 1,000 mg/kg females. 

TABLE 3. Mean (±SD) Food Consumption and Food Efficiency in Male and Female Rats 

Exposure Time Dose (mg/kg)

0 100 300 1,000

Food Consumption (g/animal/day) - Males

Day 0-1 28.5±3.3 28.4±3.6 21.4±2.5*

(↓25%)

10.0±3.4*

(↓65%)

Day 0-7 29.4±2.1 29.3±0.9 29.9±1.3 29.0±2.2

Day 7-14 31.0±1.6 30.3±1.2 32.9±0.9*

(↑6%)

33.0±1.5*

(↑6%)

Day 0-14 30.2±1.8 29.8±1.0 31.4±0.9 31.0±1.7

Food Consumption (g/animal/day) - Females

Day 0-1 18.5±3.6 17.5±3.5 14.9±2.9*

(↓19%)

5.6±2.3*

(↓70%)

Day 0-7 20.2±1.6 20.2±1.9 20.1±0.6 18.1±1.4*

(↓10%)

Day 7-14 20.3±2.1 19.9±1.8 19.8±1.5 20.2±2.0

Day 0-14 20.2±1.8 20.0±1.8 20.0±1.0 19.2±1.5

Food Efficiency (avg wt gain/avg food consumed) - Males

Day 0-1 0.156±0.101 0.124±0.167 -0.233±0.205*

(↓249%)

-1.501±1.080*

(↓1,064%)

Day 0-7 0.296±0.026 0.308±0.046 0.303±0.026 0.276±0.030

Day 7-14 0.268±0.032 0.265±0.037 0.276±0.033 0.268±0.030

Day 0-14 0.282±0.028 0.286±0.040 0.289±0.024 0.272±0.025

Food Efficiency (avg wt gain/avg food consumed) - Females

Day 0-1 -0.082±0.284 -0.011±0.366 -0.146±0.485 -3.249±5.25*

(↓3,862%)

Day 0-7 0.176±0.056 0.197±0.043 0.170±0.052 0.116±0.057*

(↓34%)

Day 7-14 0.160±0.043 0.152±0.045 0.162±0.044 0.179±0.065

Day 0-14 0.168±0.030 0.175±0.036 0.166±0.037 0.150±0.039

Values represent mean±SD, n=12.

Percent difference from the control is included in parentheses and was calculated by the Investigators. 

* Significantly different from the control group, p≤0.05.

Data were obtained from pages Tables 7 (page 38), 8 (page (39), 9 (page 40) and 10 (page 41) of the study report.

D. NEUROBEHAVIORAL RESULTS:

1. FOB findings: Significantly (p≤0.05) higher incidences of abnormal sleeping behavior were 

observed in the 1,000 mg/kg group males in the home cage on Day 7 and included limbs 

spread out or lying on one side (4/12 treated vs. 0/12 control) and palpebral closure 

commensurate with sleeping (3/12 treated vs. 0/12 control). No other treatment-related 

effects on FOB parameters were noted.

2. Locomotor activity: A summary of mean motor activity (duration and number of 

movements) in males and females is presented in Tables 4 (a and b) and 5 (a and b). Motor
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activity was affected by test substance in both males and females; however this was a 

transient effect occurring only on Day 0. The only significant (p≤0.05) differences from the 

control group were decreased total duration of movements in the 1,000 mg/kg males (↓44%) 

and females (↓56%) on Day 0. No statistically significant differences between control and 

test substance were observed in total duration of movement on Days 7 and 14 in either sex. 

The comparison of the single intervals with the control group resulted in some sporadic

significantly decreased values during the first 3 10-minutes intervals for the 1,000 mg/kg 

males (↓43-90%) and females (↓44-77%) on Day 0 (Tables 4a and b). On Day 7, mean 

duration of movement was significantly (p≤0.05) reduced by 91% and 65% (at interval 7) in 

the 300 and 1,000 mg/kg males group, respectively, but not in the females (Table 4a and b).

TABLE 4a. Selected Mean Duration of Movement (sec) for Male Rats

Dose

(mg/kg)

Successive 10-Minute Intervals

1 2 3 5 7 9 Total

Baseline

0 395±49 288±120 172±141 71±111 40±67 18±34 1120±476

100 391±55 246±108 125±134 54±92 32±47 20±45 966±399

300 387±37 229±104 108±143 91±134 49±80 36±72 1138±625

1,000 367±34 235±114 64±74*

(↓63%)

17±38 57±75 17±22 859±257

Day 0

0 396±52 190±130 84±111 21±36 15±20 32±74 848±353

100 374±56 194±121 99±117 10±9 4±5 7±7 754±322

300 369±50 150±104 47±79 9±15 21±28 24±47 671±193

1,000 227±77*

(↓43%)

47±46*

(↓75%)

8±11*

(↓90%)

39±94 44±70 23±42 479±278*

(↓44%)

Day 7

0 411±46 254±79 122±146 73±119 78±94 14±13 1163±633

100 391±45 195±70 94±117 79±111 25±47 16±27 971±446

300 399±32 260±94 111±96 37±86 7±11*

(↓91%)

43±85 957±438

1,000 403±60 297±69 126±113 15±35 27±75*

(↓65%)

36±73 1010±411

Day 14

0 382±59 262±68 156±104 88±123 63±82 37±63 1242±564

100 377±31 213±87 67±74 63±117 62±119 81±124 995±417

300 403±34 256±87 145±154 52±87 37±68 40±82 1083±565

1000 382±59 226±95 125±113 77±115 60±95 82±120 1137±448

Values represent mean±SD, n=12.

Percent difference from the control is included in parentheses and was calculated by the Reviewers. 

* Significantly different from the control group, p≤0.05.

Data were obtained from Table 15 on page 57 of the study report.

TABLE 4b. Selected Mean Duration of Movement (sec) for Female Rats

Dose

(mg/kg)

Successive 10-Minute Intervals

1 2 3 5 7 9 Total

Baseline

0 364±38 256±118 183±120 129±125 43±70 2±3 1238±562

100 375±63 263±66 176±119 114±108 39±55 51±88 1345±470

300 390±37 271±77 151±143 92±108 83±90 10±15 1237±289

1,000 373±43 249±77 147±107 152±139 56±101 27±52 1286±560

Day 0
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0 372±56 207±133 131±117 67±91 99±111 21±44 1143±563

100 361±61 185±86 91±74 77±107 88±106 12±17 1013±403

300 325±100 238±65 84±66 39±58 81±79 35±52 1000±322

1,000 210±70*

(↓44%)

80±70*

(↓61%)

30±36*

(↓77%)

29±54 34±67 12±16 508±252*

(↓56%)

Day 7

0 400±42 250±118 173±106 128±117 73±84 77±100 1464±388

100 397±64 210±91 157±135 85±115 131±138 63±84 1340±511

300 404±45 275±97 127±89 100±139 67±77 53±75 1294±376

1,000 373±76 200±113 125±104 99±95 112±89 59±106 1263±591

Day 14

0 382±42 219±84 134±87 139±107 132±122 81±94 1466±569

100 414±55 243±94 162±141 134±129 72±86 96±127 1496±564

300 373±64 255±108 237±115 100±89 29±35 63±71 1306±393

1000 356±68 190±107 111±101 140±112 91±91 64±92 1277±602

Values represent mean±SD, n=12.

Percent difference from the control is included in parentheses and was calculated by the Reviewers. 

* Significantly different from the control group, p≤0.05.

Data were obtained from Table 16 on page 58 of the study report.

The mean number of movements was unaffected by administration of test substance at 100, 

300, and 1,000 mg/kg in males or females (Tables 5 a and b). The only significant (p≤0.05) 

differences from the control was decreased mean number of movements during interval 7 in 

males at dose levels of 300 (↓84%) and 1,000 (↓60%) mg/kg and during interval 3 in the 

1000 mg/kg females (↓67%) group (Table 5 a and b). Significant decreases (p≤0.05) were 

noted on the mean duration of movement (↓63%) and number of movement (↓49%) during 

interval 3 of the baseline in the 1,000 mg/kg males group, but not in the females (Table 4 and 

5). This finding was not relevant because animals were not given test substance during the 

acclimation period (baseline).

TABLE 5a. Selected Mean Number of Movements for Male Rats

Dose (mg/kg) Successive 10-Minute Intervals

1 2 3 5 7 9 Total

Baseline

0 137±25 123±30 88±59 40±47 28±41 17±27 527±193

100 132±10 120±33 70±50 33±47 22±32 17±32 458±173

300 130±17 109±36 52±56 44±57 36±48 29±42 530±244

1,000 136±18 116±40 45±40*

(↓49%)

13±21 37±41 17±18 433±132

Day 0

0 132±20 92±49 54±63 14±17 15±15 23±43 406±168

100 138±21 102±46 59±66 10±7 7±6 9±9 381±143

300 132±23 78±46 30±42 10±7 16±17 19±26 327±81

1,000 126±37 43±35*

(↓53%)

12±12 26±39 31±36 25±30 347±146

Day 7

0 135±23 133±32 62±45 40±55 45±47 14±8 542±226

100 139±12 115±28 53±53 45±52 19±22 14±15 485±208

300 130±16 116±33 71±52 23±39 7±9*

(↓84%)

25±33 432±153

1,000 125±21 131±28 71±53 19±35 18±34*

(↓60%)

27±45 457±222

Day 14
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TABLE 5a. Selected Mean Number of Movements for Male Rats

Dose (mg/kg) Successive 10-Minute Intervals

1 2 3 5 7 9 Total

0 137±20 131±28 91±42 45±51 45±50 32±42 621±244

100 135±10 107±34 49±45 32±44 33±51 46±62 489±185

300 131±15 117±27 65±50 26±36 23±31 23±34 468±194

1000 135±13 114±35 71±56 47±61 37±44 43±54 567±267

Values represent mean±SD, n=12.

Percent difference from the control is included in parentheses and was calculated by the Reviewers. 

* Significantly different from the control group, p≤0.05.

Data were obtained from Table 17 on page 59 of the study report.

TABLE 5b. Selected Mean Number of Movements for Female Rats

Dose (mg/kg) Successive 10-Minute Intervals

1 2 3 5 7 9 Total

Baseline

0 129±17 113±31 94±49 71±57 33±43 4±3 583±220

100 132±19 127±23 99±58 74±57 36±46 36±53 702±265

300 128±12 127±33 78±59 55±50 54±45 13±14 605±128

1,000 124±12 112±26 81±44 76±64 36±56 23±39 624±308

Day 0

0 135±15 91±40 78±56 46±53 57±52 16±27 578±216

100 142±30 97±27 64±46 46±42 54±55 13±13 551±185

300 124±33 124±30 65±45 28±39 57±47 26±33 552±158

1,000 118±29 56±37 26±28*

(↓67%)

22±34 26±33 14±17 363±131

Day 7

0 136±16 108±37 106±54 69±54 43±45 45±49 712±217

100 130±17 110±31 77±47 51±54 71±59 44±47 660±198

300 133±14 131±38 86±50 51±51 50±47 42±50 661±231

1,000 122±22 102±36 70±48 61±52 68±51 36±45 621±284

Day 14

0 131±22 109±36 81±44 77±51 71±56 50±46 735±248

100 131±15 112±33 83±56 78±58 53±49 52±53 724±214

300 127±22 124±46 106±43 63±52 26±28 41±43 660±234

1000 126±22 93±40 70±52 75±47 63±58 41±51 646±304

Values represent mean±SD, n=12.

Percent difference from the control is included in parentheses and was calculated by the Reviewers. 

* Significantly different from the control group, p≤0.05.

Data were obtained from Table 18 on page 60 of the study report.

3. Rearing: The only significant (p≤0.05) difference from the control group was lower mean 

rearing (↓50%) in the 1,000 mg/kg group females, but not in the males, on test Day 0 (Table 

6). This finding was consistent with the reduction in motor activity observed in the 1,000 

mg/kg group males and females on Day 0.
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TABLE 6. Mean (±SD) Number of Rearing Movements in Female Rats 

Exposure Time Dose (mg/kg)

0 100 300 1,000

Baseline 7±3 7±2 5±1 6±3

Day 0 8±4 7±3 6±2 4±2*

(↓50%)

Day 7 9±5 8±4 7±3 8±3

Day 14 7±4 7±4 8±3 7±3

Values represent mean±SD, n=12.

Percent difference from the control is included in parentheses and was calculated by the Reviewers. 

* Significantly different from the control group, p≤0.05.

Data were obtained from Tables 12 on page 43 of the study report.

4. Forelimb and Hindlimb Grip Strength: There were no treatment-related effects on 

forelimb or hindlimb grip strength in either sex at any dose level.

5. Foot Splay: Foot splay was unaffected by the administration of test substance at 100, 300, 

and 1,000 mg/kg in males and females. There were no statistically significant differences 

between the control and test substance-treated groups.

6. Body Temperature: There were no treatment-related effects on body temperature in either 

sex at any dose level. On Day 0, mean body temperature was significantly (p≤0.05) reduced

by ↓2% in the 100 mg/kg females group. This finding was due to normal biological variation 

and was not treatment related since there was no similar effect seen in the higher doses and 

no dose relationship. On Day 7, higher (p≤0.05) body temperature was noted in the females 

(each ↑3%) at dose levels of 300 and 1,000 mg/kg (Table 7). However, this finding was not 

treatment related since the mean body temperature values were within the historical control 

data (Table 7).

TABLE 7. Mean (±SD) Body Temperature (oC) in Female Rats 

Exposure Time Dose (mg/kg)

0 100 300 1,000

Baseline 33.8±0.8 33.3±0.5 33.3±0.5 33.5±0.6

Day 0 34.2±0.9 33.4±0.8*

(↓2%)

34.0±0.9 33.5±0.7

Day 7 35.2±1.2 35.3±0.6 36.3±1.2*

(↑3%)

36.3±1.0*

(↑3%)

Day 14 34.8±0.7 35.0±1.0 34.8±1.0 35.0±0.8

Historical control data for 

female body temperature for 

day 7 #

Mean = 36.2±0.7 oC (34.8±0.8 – 37.8±0.6); n= 10-12

Values represent mean±SD, n=12.

Percent difference from the control is included in parentheses and was calculated by the Reviewers. 

* Significantly different from the control group, p≤0.05.

# Data were obtained from Appendix K on page 218-219 of the study report.

Data were obtained from Tables 12 on page 43 of the study report.

E. SACRIFICE AND PATHOLOGY:

1. Gross Pathology: No adverse, treatment-related effects were noted during gross pathology. 

The only findings noted at necropsy were dilated kidneys in 3 males at 300 mg/kg and in one 

male at 1,000 mg/kg, and small testes in one male at 300 mg/kg. Those gross findings were 
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consistent with normal background changes observed in rats of this age and strain.

2. Neuropathology: No adverse, treatment-related histological changes were noted in the 1,000 

mg/kg group males or females. 

III. DISCUSSION AND CONCLUSIONS:

A. INVESTIGATORS’ CONCLUSIONS: The investigator concluded that although transient 

decreases in motor activity were observed on test day 0 in males and females administered 

1000 mg/kg, which was also consistent with decreased rearing incidence in 1000 mg/kg 

females, there were no other effects on neurobehavioral parameters. The decreased motor 

activity and rearing incidence, however, correlate with the systemic toxicity (decreased body

weight gain, food consumption, and food efficiency) observed over the interval of test days 

0-1. For females in the 1000 mg/kg group, body weight at test day 7 and body weight gain 

over the 0-7 day interval were also statistically significantly reduced. Body weight gain over 

the 0-7 day interval was also lower in 1000 mg/kg males, but was not statistically significant. 

Therefore, the decreased motor activity and rearing incidence observed in 1000 mg/kg males 

and/or females was considered to be secondary to the systemic toxicity and was not a 

primary effect of the test substance.

Under the conditions of the study, the no-observed-adverse effect level (NOAEL) for 

systemic toxicity in males and females was 300 mg/kg based on decreased body weight gain 

over the 0-1 and 0-7 day intervals, reduced food consumption, and/or food efficiency on test 

day 1, with secondary effects on motor activity and rearing observed at 1000 mg/kg. The 

NOAEL for neurotoxicity in males and females was 1000 mg/kg based on the absence of 

corroborative effects in other neurobehavioral parameters and neuropathology.

B. REVIEWER COMMENTS: Exposure of Crl:CD(SD) rats to Tribenuron Methyl (DPXL5300) at dose levels of 100, 300, and 1,000 mg/kg bw for 14 days resulted in no death or 

clinical findings.

The only significant difference in body weights in males and females at any dose level tested 

was slightly lower body weight (↓7%) in the 1,000 mg/kg group females on Day 7, but not 

on Day 0 or Day 14. Significant body weight loss was noted in males at the dose of 300 (↓4.5 

g) and 1,000 mg/kg (↓12.2 g) over the interval test Days 0-1, compared to a 4.7 g body 

weight gain in the control group. In addition, body weight gain was significantly reduced by 

(↓42% in the 1,000 mg/kg group females on Days 0-7. Body weight gain was also decreased 

by ↓8% in the 1,000 mg/kg males on Day 0-7, but not statistically significant. It is concluded

that lower body weight in the 1,000 mg/kg females on Day 7 was correlated with the 

decreased body weight gain observed in the same females over the 0-7 day interval.

Treatment-related effects on food consumption were evident in the 300 and 1,000 mg/kg 

males and females. In males, significant decreases (p≤0.05) in food consumption were noted 

at dose levels of 300 (↓25%) and 1,000 mg/kg (↓65%) on Day 0-1. Similar to males on Day

0-1, food consumption was significantly decreased by ↓19% and ↓70% at 300 and 1,000 

mg/kg, respectively, in females. No significant differences were noted on overall (Days 0-14) 

food consumption in the 1,000 mg/kg males or females when compared to the control group. 

Significant (p≤0.05) reductions in food efficiency were noted in the 300 mg/kg and 1,000 
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mg/kg males and the 1,000 mg/kg females on Day 0-1. This reduction was correlated with 

lower food consumption observed in the 300 mg/kg and 1,000 mg/kg males and 1,000, 

mg/kg females on Day 0-1. Moreover, lower food efficiency observed in the 1,000 mg/kg 

females (↓34%) on Day 0-7 was correlated with the decreased food consumption observed in 

the 1,000 mg/kg females (↓10%) on Day 0-7.

No treatment-related neurotoxic-effects were observed. Transient, significant lower motor 

activity (duration of movement) was observed in males (↓44%) and females (↓56%) at a dose 

level of 1,000 mg/kg on Day 0, but not on Days 7 and 14. This reduction was accompanied 

by significantly decreased duration of movement during the first 3 10-minutes intervals for 

males and females on test Day 0. Total number of movements was not affected at any dose 

level. Mean number of rearing movements was significantly decreased by ↓50% in the 1,000 

mg/kg females on Day 0, but not in the males. The decreased mean number of rearing 

movements observed was correlated with the decreased total duration of movement observed 

in the 1,000 mg/kg females on Day 0. The transient effects on motor activity and rearing are 

attributed to the body weight effects, significant reductions in food consumption, and/or food 

efficiency also observed at the same dose. Significantly (p≤0.05) higher incidences of 

abnormal sleeping behavior were observed in the 1,000 mg/kg group males in the home cage 

on Day 7. However, it is unclear if this is treatment related because it was only observed on 

Day 7 in males and all other treatment related findings were observed on Day 0 or 1.

No treatment-related alterations were observed in gross histopathology observations or 

microscopic neurohistopathology in the 1,000 mg/kg male and female groups.

The LOAEL for systemic toxicity is 1000 mg/kg for males and females, based on body 

weight changes (BW loss in males, decreased BWG in females), reduced food consumption, 

and/or food efficiency, and abnormal sleeping behavior, transient effects on motor activity 

and rearing, attributed to the systemic changes observed.

This study is classified as acceptable/guideline and satisfies the guideline requirement 

(OPPTS 870.6200a; OECD 424) for an acute neurotoxicity study in rats.

C. STUDY DEFICIENCIES:

No deficiencies were reported in this study.