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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 8 December 1980 to 19 March 1981
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study run to a reliable method but not to GLP and no guideline followed. However it has been inspected and audited by QA

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1985
Report Date:
1985

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
Principles of method if other than guideline:
Five groups of 20 male and 20 female rats of the Fischer 344 strain were dosed at concentrations of the test substance in the diet calculated to give dose levels of 50, 150, 450, 1350 or 4000 mg test substance/kg/day for male rats and 50, 115, 270, 620 or 1500 mg test substance/kg/day for female rats. One group of 20 male and 20 female rats received untreated diet and acted as contemporary controls. Study duration was 13 weeks, at the end of this period animals were killed and subjected to full necropsy.
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: crystalline
Details on test material:
Batch No.: not specified
Purity: not specified

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River U.S.A. via Charles River (U.K.) Limited, Manston, Kent, England
- Weight at study initiation: 40-60 g
- Housing: Rats were housed in a barrier maintained animal room. Rats were housed one animal per cage in suspended polypropylene cages (overall dimensions ca 480 x 150 x 120 mm) with stainless steel wire grid tops and bottoms. Each cage had a polypropylene water bottle (total capacity 300 mL) with rubber washer and melamine cap.
- Diet (e.g. ad libitum): rodent diet, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum
- Acclimation period: 10 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21°C ± 2°C
- Humidity (%): ca. 50%
- Air changes (per hr): 14 air changes/hour
- Photoperiod (hrs dark / hrs light): 12 h light/dark cycle

IN-LIFE DATES: From: 8 December 1980 To: 19 March 1981

No additional data

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
DIET PREPARATION
- Rate of preparation of diet (frequency): Fresh diets were prepared once each week.
- Mixing appropriate amounts with (Type of food): The concentration of test compound was adjusted each week to give as constant a mg/kg/day level as possible by prediction of mid-week body weight and weekly food consumption for the week in question.
Diets were prepared by direct admixture of the required amount of the test substance to diet and blending for 20 min in a Winkworth change drum tumble mixer.

No additional data
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
A 100 g sample of diet from each group/sex was taken and retained immediately after diet preparation at the beginning of each study week. In addition, 4 samples of 100 g were taken from each group/sex at the beginning of Weeks 1, 2, 3, 4, 7, 10 and 13. The latter samples were analysed for test substance levels.

A suitable weight of diet (2.5 g or 5 g) was weighed accurately into clean glass 8 oz jars. To this was added I ml of internal standard solution (dinitrobenzene in acetonitrile at a suitable concentration) and 50 ml of acetonitrile as extracting solvent. The jars were shaken mechanically for 1 h then left to settle, preferably overnight. A suitable aliquot was transferred to a sample vial and analysed by HPLC.

Standard solutions of test substance were prepared by adding a known amount of test substance (equivalent to that of the group being analysed) to a sample of untreated diet. These were treated with internal standard solution and extracting solvent as described for the formulated diet samples.

Three quality control samples were included with each batch of test samples and standards. For this purpose a solution of the test substance in acetonitrile was prepared by an independent analyst and these solutions used by the analyst to spike blank diet samples in exactly the same way as the standards.

HPLC Conditions
Instrument: Hewlett Packard 1084B with variable wavelength detector and automatic sampler.
Column: 100 x 5 mm stainless steel packed with ODS Hypersil (5 μ).
Solvent: Acetonitrile : Water (40:60 v/v).
Flow: 1.5 mL/min
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
at least 91 consecutive days
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
Male: 50, 150, 450, 1350 or 4000 mg test substance/kg/day; Female: 50, 115, 270, 620 or 1500 mg test substance/kg/day
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
Male: 51.0, 153.5, 461.0, 1394.6 or 4101.3 mg test substance/kg/day; Female: 50.3, 115.6, 273.3, 627.7 or 1511.9 mg test substance/kg/day
Basis:
actual ingested
No. of animals per sex per dose:
20 animals per sex per dose
Control animals:
yes, plain diet
Details on study design:
None stated
Positive control:
None stated

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice a day

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: The weight of each animal was recorded at weekly intervals commencing one week before the start of treatment up until the end of treatment. In addition, animals were also weighed on Day 4 of the first 4 weeks.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: Water consumption was assessed visually for any intergroup differences.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: before dosing commenced and during Week 13 of dosing
- Dose groups that were examined: all animals

HAEMATOLOGY: Yes
- Time schedule for collection of blood: during Weeks 5 and 12 of treatment
- Anaesthetic used for blood collection: Yes (light ether)
- Animals fasted: No data
- How many animals: 10 males and 10 females from top and control groups

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: during Weeks 5 and 12 of treatment
- Animals fasted: No data
- How many animals: 10 males and 10 females from top and control groups

URINALYSIS: Yes
- Time schedule for collection of urine: Collections of individual urine samples were made over a 4 h period of food and water deprivation during Weeks 5 and 12 of dosing.
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data

NEUROBEHAVIOURAL EXAMINATION: No data

OTHER: Pharmacokinetic Sampling: Blood samples were obtained at post mortem by the removal of at least 3 mL whole blood via the caudal vena cava into heparinised tubes. Samples were taken from 5 male and 5 female animals selected at random from each group. These samples were centrifuged and the plasma deep frozen and stored at IRI.

No additional data
Sacrifice and pathology:
GROSS PATHOLOGY: Yes, All animals which died or were sacrificed were necropsied. The gross dissection and necropsy was performed under the supervision of a pathologist. The necropsy is defined as external examination including body orifices, weighing of the following tissues: Brain, Heart, Kidney, Ovaries, Liver, Lungs, Testes, Adrenals, Spleen
HISTOPATHOLOGY: Yes, examination and fixation of the following tissues: Brain, Spinal cord, Peripheral nerve (sciatic), Eyes, Pituitary, Thyroid, Parathyroid, Salivary glands (submaxillary), Heart, Lungs, Spleen, Liver, Pancreas, Adrenals, Lymph nodes (mesenteric cervical submaxillary bronchial), Kidneys , Bladder, Testes (plus epididymides), Prostate, Ovaries (minus fallopian tubes), Uterus, Fallopian tubes, Stomach, Small intestine (duodenum jejunum ileum), Large intestine (caecum colon rectum), Skeletal mucle (thigh), Skin (abdominal), Mammary gland, Any gross lesions e.g. tissue masses, suspected tumours (including surrounding normal tissue), Sternum, Adipose tissue (perirenal), Nasal tubinate, Trachea, Thymus (where possible)
Other examinations:
None stated
Statistics:
Statistical evaluation of quantitative data was performed where it seem appropriate. Males were treated independently of females. The level of probability chosen as significant was P<0.05, but in any case the actual level is reported. For evaluation of mean differences a "two tail" distribution was used.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
no effects observed
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
no effects observed
Details on results:
Clinical Signs and Mortality:
None was observed which could be attributed to dosing with the test substance.
Only 3 premature deaths occurred during the study, all from different treatment groups.

Body Weight:
Body weight gains were reduced in male and female animals receiving test substance in dose related fashion.

Food Consumption:
Food consumption trends were variable throughout the study but treated groups consumed less food than untreated groups during dosing.

Water Consumption:
Visual assessment of water consumption revealed no intergroup differences.

Ophthalmic Examination:
No abnormalities were detected which could be attributed to dosing with the test substance.

Haematology:
(i) Significant reductions in haemoglobin (Hb) levels and packed cell volume (PCV) (P<0.001) in males and females receiving 4000 and 1500 mg test substance/kg/day respectively were seen. Other parameters fell within normal ranges except for isolated cases.
(ii) Significant reductions were seen in Hb, PCV and red blood cell (RBC) levels (P<0.01) in females receiving the high dose level of the test substance, with corresponding reductions, though not significant, in the same parameters in males. Slight rises in methaemoglobin in both males and females receiving high dose of the test substance were seen, significant (P<0.05) in males only. Female white blood cell (WBC) count was significantly raised (P<0.05) probably reflecting significant increases (P<0.05) in neutrophils.

Clinical Chemistry:
(i) There were increased alkaline phosphatase levels in males and a marginal increase in females (P<0.01 in males only) receiving 4000 or 1500 mg test substance/kg/day. There was also a reduced ALT level in males receiving 4000 mg test substance/kg/day (P<0.01). A significant increase was also seen in BUN levels of females receiving 1500 mg test substance/kg/day. Albumin levels were also increased in males receiving 4000 mg test substance/kg/day (P<0.001). Except for isolated cases other parameters were considered to fall within normal reference ranges.
(ii) Significant increases were seen in AP levels in males (P<0.001) and females (P<0.05) receiving the top dose level of the test substance and also in albumin levels in females (P<0.001). The male control value for AP was rather lower than normally anticipated for animals of this age and thus the results should be interpreted with caution. Total protein levels of females receiving 1500 mg test substance/kg/day also showed a slight increase (P<0.05) in line with the raised albumin levels. BUN levels were also raised significantly (P<0.001) in females receiving 1500 mg test substance/kg/day. Other parameters were considered to be within normal ranges except for isolated cases.

Urinalysis:
(i) Females rats receiving 1500 mg test substance/kg/day showed a reduced pH and specific gravity (SG) with a corresponding increase in urinary volume. Males did not show this trend. Other parameters were considered to fall within normal ranges.
(ii) Female rats receiving 1500 mg test substance/kg/day showed a reduced pH and SG with a corresponding increase in volume. In addition to this effect fern-like crystals were noted in urine of males and females receiving 4000 or 1500 mg test substance/kg/day but not in controls.

Organ weights:
The following changes were seen: Significantly reduced absolute and relative adrenal weights in all treated male groups with an increase in female groups. Relative brain weight increased in males and females receiving 4000 or 1500 mg Htest substance/kg/day. Absolute brain weights increased in top dose females. Absolute heart weights increased in male and female top dose rats.
Female treated rats showed a dose related increase in relative kidney weights.
Males showed reduction in absolute and relative spleen weights. Relative liver and lung weights increased in treated females. Females showed reductions in absolute spleen and ovary weights.

Gross and Histopathological:
No macroscopic lesions were observed which could be attributed to dosing with the test substance. There were a number of lesions found on histopathological examination of the 2 highest dose and control groups but these were consistent with the age and strain of rats.
There were, however 2 lesions found which exhibited a dose related trend. These were found in liver and kidneys which were recognised as target organs and histopathologically examined in all other animals (see below).
Toxic changes in the liver were characterised by enlarged cells, mainly in centrilobular areas, with large, pale nuclei and dark, granular, eosinophilic cytoplasm. In some areas there was dilation of the sinusoids and small foci of necrosis.
This liver effect was most marked in males, all males receiving 450 or 4000 and 90% of males receiving 1350 mg test substance/kg/day exhibiting the condition.
Only one female receiving 270 mg test substance/kg/day showed the effect.
Tubular changes in kidneys were seen mostly in females receiving the higher dose levels of the test substance and were characterised by focal atrophy and dilation of the tubules. Males also exhibited this condition but to a considerably lesser extent and one female control rat also showed this change.

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
ca. 51 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: Significant toxic liver changes in males receiving 150 or more mg HMX/kg/day
Dose descriptor:
NOAEL
Effect level:
ca. 115.6 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
female
Basis for effect level:
other: Tubular kidney changes in females receiving 270 or more mg HMX/kg/day.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

From Henderson, 1985:

No significant increase in plasma levels of the test substance was observed with increasing dose.

The data may well indicate that most of the administered the test material was not systemically absorbed but was excreted unchanged.

The presence of the test substance in the plasma of the control group animals was also indicated. The levels were low but significant. They may approximate to those anticipated following a single dose of 13 -15 mg/kg. The reason why the plasma from the control group animals should have contained the test substance are unknown.

Henderson 1985. HMX: Analysis in Plasma Obtained After 90 Day Toxicity Studies with Rats and Mice

Insufficient plasma was available for successful analysis of the test substance in mouse plasma at the termination of the 90 day mouse toxicity study. Inveresk Research International Limited Musselburgh, EH2l 7UB, Scotland. IRI Projects 415669 AD, 415669 AR, 415669 AM

Applicant's summary and conclusion

Conclusions:
Dosing of test substance to male and female F344 rats for 90 days via the diet results in a slight reduction in red cell parameters and possible methaemoglobinaemia. The most significant changes were toxic liver damage in male rats at doses of 150 mg test substance/kg/day and above and renal tubular damage in female rats at 270 mg test substance/kg/day and above. Other effects were of doubtful significance or most likely to be secondary to the hepatic and renal damage.
The NOAEL of the test substance to female Fischer 344 rats is 115.6 mg/kg bw/day (actual dose). The NOAEL of the test substance to male Fischer 344 rats is 51.0 mg/kg bw/day (actual dosel).