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Toxicological information

Basic toxicokinetics

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basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1986-06-09 to 1986-07-11
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No GLP is claimed. The proprietary study is not according to the regulatory guideline, but is similar and provides relevant information.

Data source

Reference Type:
study report
Report Date:

Materials and methods

Objective of study:
Test guideline
equivalent or similar to
OECD Guideline 417 (Toxicokinetics)
Principles of method if other than guideline:
The purpose of the study was to determine the distribution, concentration and clearance of radio-labelled TMA, and/or its metabolites in rats following a single inhalation exposure.
GLP compliance:
not specified

Test material

Details on test material:
- Name of test material (as cited in study report): 14C-Trimellitic Anhydride, 14C-TMA
- Lot/batch No.: 2031-236
- Radiochemical purity (if radiolabelling): 97%
- Specific activity (if radiolabelling): 13.5 mCi/mmol
- Locations of the label (if radiolabelling): the radiolabel was in the 2-carbonyl position
- Storage condition of test material: Stored in tightly sealed opaque plastic jars in a ventilated cabinet, at room temperature (approximately 22°C)

Test animals

Details on test animals and environmental conditions:
The test animals were male and female Sprague-Dawley rats, weighing approximately 135 g, were purchased from Charles River Breeding Laboratories (Portage, MI). The rats were acclimatised for 2 weeks, during which time they were examined to ensure their health and suitability as test subjects. Individuals were identified by metal ear tags and cage cards.
Purina Rodent Chow 5001 and water (reverse-osmosis purified) were available ad libitum.
During the exposure the rats were singly housed in disposable handmade wire cages. Following the exposure the rats were double housed in disposable plastic cages containing San-I-Cel corn cob bedding. Animal rooms were maintained at approximately 22°C and 40% relative humidity. Fluorescent lighting was provided on a 12 hour light/dark cycle.

Administration / exposure

Route of administration:
inhalation: dust
unchanged (no vehicle)
Details on exposure:
All rats were exposed once for a 45 minute period to 14C-trimellitic anhydride (14C-TMA) at a target concentration of approximately 950 µg/m³. A static test atmosphere was generated by periodically feeding small amounts of the test article into the chamber via a partially encased recirculating blower. Food and water were not available during the exposure period.
The exposure was conducted in a 370 litre glass aquarium fitted with a plexiglass top. The entire chamber was housed in a PVC bag to serve as secondary containment, and this was then contained in a large PVC tent to serve as tertiary containment.
Analytical exposure concentrations were determined by drawing a known volume of the test atmosphere across an open-face filter, the contents of the filter with then analysed with HPLC.
Duration and frequency of treatment / exposure:
Single 45 minute exposure
Doses / concentrations
Doses / Concentrations:
The target concentration was approximately 950 µg/m³ (a concentration sufficient to approximate a delivered dose of approximately 50 uCi of 14C per rat).
No. of animals per sex per dose:
14 males and 14 females
Control animals:
Positive control:
A positive control was not included and is not required for this study type.
Details on study design:
Rats were randomly allocated to treatment groups. All rats were observed during the exposure for morbidity and mortality and at least once per day. All rats were weighed immediately prior to exposure, weekly thereafter, and at necropsy. The designated rats were euthanised at scheduled intervals and subjected to an extensive necropsy.
Details on dosing and sampling:
At 3 hours, and 1, 2, 4, 8, 16, and 32 days following the exposure period two male and two female rats were euthanised and necropsied. The following tissues/fluids/excreta were collected at necropsy and analysed for 14C content: popliteal lymph nodes, lung-associated lymph nodes (LALN), lungs, trachea, thymus, whole blood, serum, brain, heart, spleen, liver, kidneys, intestines, stomach, urinary bladder, gonads, urine, faeces, skin, abdominal skin and fat, bone marrow, pancreas, oesophagus, adrenals, spinal cord, bone marrow and leg muscle.

The designated tissues were weighed, homogenised, and 100 mg aliquots were dissolved with 0.1 ml of Scintigeset in liquid scintillation vials. The dissolved tissue samples were neutralised with HCl and decolourised with 30% H2O2. The vials were filled with 5 ml of Scinti Verse and the 14C content was analysed in a liquid scintillation counter.

Serum was collected and analysed for TMA-specific antibodies. The method quantified the total amount of specific serum antibody against TMA, but not the antibody class.
The elimination rate constant (Ke) was determined by plotting the natural log (Ln) of the counts per minute (cpm) per gram of tissue versus the time since exposure, and then performing a linear fit. Linear regression of the curve yielded a straight line, the negative slope of which equalled the Ke. The half life (t-1/2) of the 14C was calculated for each tissue using t-1/2= 0.693/Ke

Results and discussion

Preliminary studies:
No preliminary data reported.
Main ADME resultsopen allclose all
Rapid absorption was seen under the conditions of this study
Radiolabel was detected in all tissues examined, including the pulmonary and cardiovascular systems, and the gastrointestinal tract. Accumulation was noted in the kidneys, urine, bladder, faeces, and oesophagus.
Faecal and urinary excretion was noted

Toxicokinetic / pharmacokinetic studies

Details on absorption:
Carbon-14 was distributed to all tissues examined with particular accumulation occurring in the kidneys, urine, bladder, faeces, and oesophagus.
Details on distribution in tissues:
The peak concentrations of 14C in the tissues were found at the first time point examined (3 hours post-exposure). The concentrations of 14C decreased rapidly in all tissues after 3 hours in an approximate exponential fashion. The exponential decline in 14C concentration was apparent in all tissues except for the lung-associated lymph nodes, where there appeared to be an initial decline followed by a second influx of 14C peaking at day 8 before declining again. This second peak was particularly apparent in males.
Details on excretion:
Half-life values were lowest for faeces, intestines, stomachs and oesophagi, and highest for popliteal and lung-associated lymph nodes, spleens, hearts. adrenals, brains and bone marrow. Large differences in half-life values were seen between males and females in the popliteal and lung-associated lymph nodes, bone marrow and heart.
Toxicokinetic parametersopen allclose all
Test no.:
Toxicokinetic parameters:
half-life 1st: ranged from 4 to 23 days in males
Test no.:
Toxicokinetic parameters:
half-life 1st: ranged from 3 to 46 days in females

Metabolite characterisation studies

Metabolites identified:
Details on metabolites:
Not investigated

Any other information on results incl. tables

No deaths or treatment-related clinical signs occurred during the study. The actual concentration of 14C-TMA in the exposure chamber was 950 µg/m³. All rats gained weight during the study. The radiolabel appeared in all tissues examined, including the pulmonary and cardiovascular systems, and the gastrointestinal tract. Almost all tissues exhibited an exponential elimination of 14C. The exception was the lung-associated lymph node (LALN) elimination in male rats. In this case, the 14C content declined but then increased and reached a second maximum 8 days after the exposure. This second increase was not evident in females. The second and selective increase in male LALN 14C may indicate that male rats have more antigen translocated to the LALN. Consequently, more antibody of the isotype which causes lung lesions may be produced by males. However, this hypothesis is speculative since the number of rats per time point was small. Serum antibody analysis, specific against TMA but not isotype specific, showed that there was no significant antibody present until between 4 and 8 days after the exposure. Between 8 and 32 days after the exposure, at least 2 of the 12 remaining rats developed antibody and were presumably sensitized to TMA. Thus a single short-term inhalation exposure to TMA was sufficient to sensitize at least 17% of the rats. Antibody production appeared to be greater in females than in males which confuse the male LALN previous discussion. However, it is not known what antibody isotype is actually responsible for lesions and while females may have more antibody, it may be of the wrong isotype.

Applicant's summary and conclusion

Interpretation of results (migrated information): no bioaccumulation potential based on study results
Groups of rats exposed to 14C-TMA exhibited typical first order exponential decays of 14C with half-lives ranging from 3 to 46 days. Carbon-14 was distributed to all tissues examined with particular accumulation occurring in the kidneys, urine, bladder, faeces, and oesophagus.
Executive summary:

14C - trimellitic anhydride (14C-TMA) was administered by inhalation at a concentration of approximately 950 ug/m3 during a 45 -minute period to fourteen male and fourteen female Sprague-Dawley rats. At 3 hours, and 1, 2, 4, 8, 16, and 32 days following the exposure period two male and two female rats were euthanized and necropsied. The major tissues were collected and analysed for 14C content.

No deaths occurred during the study. Maximum concentrations of tissue 14C were achieved 3 hours after the exposure, after which time most tissues displayed an exponential first order decay of 14C. The 14C content in male lung-associated lymph nodes appeared to reach a second maximum 8 days after the exposure, possibly indicating a sex-specific translocation of 14C, resulting in increased lung toxicity previously reported in male rats.

Apparent elimination rate constants (Ke) ranged from 0.015 in popliteal lymph nodes from female rats to 0.214 in faeces from female rats. In male rats, elimination rate constants (Ke) ranged from 0.030 in the heart and testes to 0.196 in faeces. Consequently biological half-life values ranged from 3 to 46 days in females, and 4 to 23 days in males. Large differences in biological half-life values between male and female rats were calculated for the popliteal and lung-associated lymph nodes, bone marrow and heart. Other sex differences in biological half-lives were minimal. TMA-specific serum antibody remained at background levels through the first 4 days, however, two rats developed significant antibody levels beginning at day 8. Thus it appeared that a single 45 -minute inhalation exposure to TMA resulted in approximately 17% of the rats becoming sensitized.