Pentane-2,4-dione

Repeated dose toxicity: dermal

Administrative data

Endpoint:

short-term repeated dose toxicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Conduction and documentation of study acceptable. Literature reference and study report available.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Reference 2

Reference Type:

secondary source

Title:

Unnamed

Year:

2001

Reference 3

Reference Type:

publication

Title:

Unnamed

Year:

2001

Materials and methods

Principles of method if other than guideline:

New Zealand White rabbits were treated by 6 h occluded cutaneous application with undiluted 2,4-pentanedione at dose volumes of 0.25, 1.0 and 1.5 mL/kg bw (corresponding to 244, 975, 1463 mg/kg bw). Animals in the control group received occluded applications of Milli-Q filtered water at a volume of 1.5 mL/kg bw. The test or control substance was applied to the clipped dorsal surface of the rabbits. Twelve animals/sex/group were used for the control and high dose groups, 6 animals/sex/group for mid and low dose groups. The original study design included dosing for 5 days the first week and 4 day the second week. The additional 6 animals/sex/group in the controls and the high dose group were used for a 4 week recovery period. Due to mortality and signs of toxicity observable in mid and high dose groups, dosing was discontinued for these groups after day 4. Three surviving males and 2 surviving females from the high dose group were euthanized on day 4 while an additional 4 males and 3 females were retained without further dosing to day 12. Rabbits in the low dose group continued to receive a total of 9 doses (5 in the first week, 4 in the second). On day 12, 6 rabbits/sex from the control group were removed from the study since they were not required for their intended purpose as a recovery group. All other surviving rabbits were euthanized on day 12. Only 3 rabbits/sex from the control group were subjected to necropsy and histopathology. Monitors for toxicity included observations for clinical signs, including skin irritation, food consumption, water consumption, body weight and body weight change, organ weights, gross pathology and histopathology.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Details on test material:

Purity: >98%
Lot No.: 0335033-007
Physical state: liquid
Storage: room temperature

Test animals

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: HRP, Inc . (Denver, PA)
- Age at study initiation: 15-18 weeks
- Weight at study initiation: 2.5 - 3.0 kg
- Fasting period before study:
- Housing: individual housing in stainless steel wire mesh cages
- Diet: Agway Prolab animal diet rabbit (Agway Inc.), ad libitum
- Water: ad libitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 16-21
- Humidity (%): 40-60
- Air changes (per hr):
- Photoperiod: 12 hrs dark / 12 hrs light

Administration / exposure

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on exposure:

TEST MATERIAL
- Amounts applied: 0.25, 1, and 1.5 mL (244, 975 and 1463 mg/kg bw)
- Constant volume or concentration used: no

TEST SITE
- Type of wrap if used: gauze pads
- Time intervals for shavings or clipplings:

REMOVAL OF TEST SUBSTANCE
- Washing: After exposure the back of the animal was wiped with a damp cloth.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

9 days

Frequency of treatment:

6 h/day

Doses / concentrations

Remarks:

Doses / Concentrations:
244, 975 and 1463 mg/kg bw
Basis:
nominal per unit body weight

No. of animals per sex per dose:

6

Control animals:

yes

Examinations

Observations and examinations performed and frequency:

Monitors for toxicity included observations for clinical signs, including skin irritation, food consumption, water consumption, body weight and body weight change, and organ weights.

Sacrifice and pathology:

3 rabbits/sex from the control group were subjected to necropsy and histopathology. Monitors for toxicity included observations for clinical signs, including skin irritation, food consumption, water consumption, body weight and body weight change, organ weights, gross pathology and histopathology.

Statistics:

The data for quantitative continuous variables were intercompared for the 3 treatment groups and the control group by use of Levene's test for equality of variances, analysis of variance (ANOVA), and t-tests. The t-tests were used when the F value from the ANOVA was significant. When Levene's test indicated similar variances, and the ANOVA was significant, a pooled t-test was used for pairwise comparisons. When Levene's test indicated heterogeneous variances, all groups were compared by an ANOVA for unequal variances followed, when necessary, by a separate variance t-test for pairwise comparisons.
Nonparametric data were statistically evaluated usinq the Kruskal-Wallis test followed by the Mann-Whitney U-test. Incidence data were compared using Fisher´s Exact Test. For all statistical tests, the probability value of < 0.05 (two-tailed) was used as the critical level of significance.

Results and discussion

Results of examinations

Details on results:

Occluded cutaneous dosing of rabbits with 2,4-pentanedione for 3 or 4 days resulted in death of 5/12 males and 7/12 females in the 1 .5 mL/kg bw (1463 mg/kg bw) group and 1/6 males and 3/6 females in the 1.0 mL/kg bw (975 mg/kg bw) group. Skin irritation was observed in all dose groups. Time to onset and severity of skin irritation were generally dose-dependent and persistent in all dose groups. Signs of skin irritation included erythema, edema, desquamation/exfoliation, excoriation, fissuring, necrosis and/or ecchymosis . In the mid and high dose groups of rabbits during the first few days of the study, several signs of systemic toxicity were evident. Numerous animals from these dose groups were hypoactive, uncoordinated and/or prostrate, had tremors, salivation, gasping and/or convulsions, and some had blue cutis of the nasal area suggestive of cyanosis. Furthermore, these groups lost mean body weight and food consumption decreased during the first few days of the study. After cessation of dosing in these dose groups, mean food consumption generally returned to control values while mean body weight gains were increased over control values. Excessive vocalization, slow or laboured breathing, and/or red perioral discharge were also observed in some high dose group animals until cessation of dosing. In the low dose group there were no mortalities, clinical signs of systemic toxicity, or effects on body weight or food consumption. Gross and microscopic evaluation at both day 4 and 12 confirmed dose-related skin irritation in all treatment groups. Microscopic lesions included acanthosis, subcutaneous edema, dermatitis, hemorrhage, congestion and/or necrosis. There were also numerous rabbits with hemorrhaging in various sections of the brain, including the meninges. Additionally, a number of brain sections showed neuronal degeneration, including the hypothalamus, mid brain, piriform cortex, pons and/or hippocampus. At both day 4 and 12, the thymus or thymic region, spleen, and/or lymph nodes of several animals of both sexes from the mid and high dose groups were congested and/or hemorrhaged; some animals also had lymphoid depletion or necrosis. This observation, combined with decreased lymphocyte and eosinophil counts in the high dose group at day 4, suggested possible effects on the immune system. Since the animals from the mid and high dose group had severe skin irritation and many signs of systemic effects a definitive conclusion regarding a treatment related response to the immune system is not possible, as discussed by the study authors. Except clinical pathology changes that may have been related to the skin irritation, no substance related differences from controls were reported in the low dose group.
According to the systemic effects observed, 244 mg/kg bw and 975 mg/kg bw correspond to the NOAEL and LOAEL of this dermal study, respectively.

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

244 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

2

Dose descriptor:

LOAEL

Effect level:

975 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Mortality occurred.

Target system / organ toxicity

Critical effects observed:

not specified