4-methyl-m-phenylene diisocyanate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to OECD 417 guideline study (GLP), pure dried corn oil used as dosing vehicle may have resulted in degradation of TDI to unidentified producs.

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Unnamed

Year:

1994

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Objective of study:

absorption

distribution

excretion

metabolism

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

4-methyl-m-phenylene diisocyanate

EC Number:

209-544-5

EC Name:

4-methyl-m-phenylene diisocyanate

Cas Number:

584-84-9

Molecular formula:

C9H6N2O2

IUPAC Name:

2,4-diisocyanato-1-methylbenzene

Details on test material:

Unlabeled TDI:
- Name of test material (as cited in study report): 14C-labeled toluene 2,4 diisocyanate
- Analytical purity: 97.72%
- Isomers composition: 200:1 (2,4-TDI : 2,6-TDI)
- Lot. No.: 28F0167
- Supplier: Sigma Chemical Company (St. Louis, USA)

Radiolabeled TDI:
- Lot. No.: 089F9246
- Radiochemical purity (if radiolabeling): >95% (range throughout the study 94.6%-100%)
- Specific activity (if radiolabeling): 23.7 mCi/mmol
- Locations of the label (if radiolabeling): Uniformly ring labeled
- Supplier: Sigma Chemical Company (Milwaukee, USA)

Radiolabelling:

yes

Remarks:

14C-labeled

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratory, Kingston, NY, USA
- Weight at study initiation: approximately 200 g
- Individual metabolism cages: yes
- Acclimation period: one week

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 h/ 12 h

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: pure dried corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The radiotracer was diluted with non-radiolabeled 2,4-TDI to obtain a target radioactivity and concentration of 72.5 µCi and 21.7 mg/g of dosing solution, respectively. The dosing solution was prepared in a controlled atmosphere glove box under a dry N2 atmosphere. The dosing solution was analyzed for radioactivity via liquid scintillation counting. In addition, weighed aliquots (200 µl) of the dose solution were derivatized with 0.5 ml piperidine in 2 ml toluene (1 hr, room temperature). The resulting 14 C-2,4-TDI-dipiperdyl derivative was then isolated by evaporation of the excess reagents and solvent (N2 stream) and reconstituted in acetone:acetonitrile:water. The samples were then analyzed by HPLC. The 14C-2,4-TDI dose solution contained 111% and 98% of target radioactivity and concentration, respectively.

VOLUME OF ADMINISTRATION
3ml/kg bw.

VEHICLE
- Justification for use and choice of vehicle (if other than water): TDI readily reacts with water

Duration and frequency of treatment / exposure:

Single exposure

Doses / concentrations

Remarks:

Doses / Concentrations:
60 mg/kg bw

No. of animals per sex per dose / concentration:

7 (4 animals were sacrificed 2 h after exposure, 3 animals 48 h after exposure)

Control animals:

no

Details on study design:

Groups of male rats were administered 14C-2,4-TDI orally at a target dose of 60 mg/kg of body weight. Following oral administration of 14C-2,4-TDI, three rats were housed in glass Roth-type metabolism cages and urine, feces, expired 14 C-volatile organics
and 14C02 were trapped for up to 48 hr and analyzed for radioactivity. At 48 hr post-dosing the rats were sacrificed, and selected tissues were collected and analyzed for radioactivity. Pooled urine specimens were analyzed by high performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS). An additional group of four rats were administered 14C-2,4-TDI orally and were sacrificed at approximately 2 hr post-dosing (peak14C blood concentration) and selected tissues were collected and analyzed.

Details on dosing and sampling:

- Body fluids sampled: urine, faeces, cage washes
- Tissues sampled: blood, fat, gastrointestinal tract, gastrointestinal tract contents, fat, kidney, liver, lung, skin and the remaining carcass.
- Time and frequency of sampling: Urine 12 h intervals, feces 24 h intervals, expired air 24 h
- From how many animals: samples pooled from 3 animals

ANALYTICAL METHODS USED
Urine:
- Liquid Scintillation Counting (LSC): determination of the overall radioactivity
- High Performance Liquid Chromatography (HPLC): Separation of the urinary metabolites
- Gas-Chromatography/ Mass Spectrometry (GC/MS): structural identification of the monoacetyl-TDA metabolite
- Gas-Chromatograpy/ Mass-Spectrometry/Mass Spectrometry (GC/MS/MS): for determination of the acetylated metabolites Feces, Air, Tissues:
- Liquid scintillation counting (LSC): determination of the overall radioactivity

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

- Orally administered 14C-2,4-TDI is not very well absorbed. The minimum estimate for absorption was 12%, which assumed that the radioactivity recovered in the feces ca. 81% represented unabsorbed material.

Details on distribution in tissues:

2 h after application most of the radioactivity was found in the GI tract and GI content (GI tract: 10.1%, GI content: 65.8%) after 48 h most of the radioactivity was excreted from the system (table 1).

Details on excretion:

The rats eliminated approximately 8% of the radioactivity in the urine and cage wash while 4% was recovered in the tissues and carcass and roughly 81% in feces (table 2)

Toxicokinetic parameters

Toxicokinetic parameters:

half-life 1st: 7.5 h for urinary excretion

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

Monoacetyl 2,4-TDA, Diacetyl 2,4-TDA and free 2,4-TDA was detected in urine (see table 3).
65% of quantitated urinary metabolites existed as acid labile conjugates.

Any other information on results incl. tables

Table 1: Total percentage of administered 14C-2,4 -TDI in tissues of male rats 2 h and 48 h after single dosing

	Percentage of administered dose 2 h after application	Percentage of administered dose 48 h after application
Blood	not analysed	0.046 ± 0.017
Carcass	5.497 ± 3.615	0.774 ± 0.2
Fat	0.002 ±  0.002	0.002 ± 0.001
Kidney	0.077 ± 0.017	0.023 ± 0.002
liver	0.499 ±  0.145	0.109 ± 0.004
Lung	0.063 ± 0.1	0.003 ± 0.22
Skin	1.122 ±  0.53	0.149 ± 0.22
GI tract	10.103 ±  3.085	0.104 ± 0.54
GI content	65.821 ± 8.346	2.560 ± 0.838
Total	83.184 ±  7.185	3.770 ± 0.867

Table 2: Distribution of radioactivity 48 h after male fisher rats were given an oral dose of 60 mg 14C-2,4 -TDI/kg bw

	Percentage of administered dose
Urine	8.38 ± 0.41
Feces	80.67 ± 5.3
Tissue&Caracass	3.77± 0.87
CO2	not quantifiable
14C volatile organics	not quantifiable
Cage wash	0.99 ± 0.52
Recovery	93.8 ± 4.32

Table 3: Concentration of Monoacetyl, Diacetyl and free 2,4 -TDA expressed as 2,4 -TDA equivalents in the 0 -12 h urine specimen following oral exposure to 14C-2,4 -TDI

	µg equivalents 2,4-TDA/ g urine
Monoacetyl 2,4-TDA	5.12
Diacetyl 2,4-TDA	8.17
Free 2,4-TDA	2.08
free + acetylated  2,4-TDA	15.37