m-tolylidene diisocyanate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1977

Report date:

1977

Materials and methods

Objective of study:

absorption

excretion

metabolism

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Deviations:

yes

Remarks:

Study performed before guideline. Various deviations but study valid for assessment.

GLP compliance:

no

Remarks:

GLP was not compulsory at the time the study was conducted.

Test material

Test material information

Constituent 1

Reference substance name:

m-tolylidene diisocyanate

EC Number:

247-722-4

EC Name:

m-tolylidene diisocyanate

Cas Number:

26471-62-5

Molecular formula:

C9H6N2O2

IUPAC Name:

2,4-diisocyanato-1-methylbenzene, 2,6-diisocyanato-1-methylbenzene

Details on test material:

- Name of test material (as cited in study report): TDI
- Physical state: liquid
- Isomers composition: 83.7% 2,4-TDI : 16.3% 2,6-TDI
- Specific activity (if radiolabelling): 38 mCi/mM
- radiochemical purity was assayed by GC, and the compound was stored in solution in benzene.

Specific details on test material used for the study:

RADIOLABELLING INFORMATION
- Specific activity: 38 mCi/mM

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: stored in solution in benzene.

OTHER SPECIFICS:
- Isomers composition: 83.7 % 2,4-TDI : 16.3 % 2,6-TDI

Radiolabelling:

yes

Remarks:

14C

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River
- Weight at study initiation: 300 ± 10 g
- Individual metabolism cages: yes
- Acclimation period: 48 h

Administration / exposure

Route of administration:

inhalation: vapour

Vehicle:

other: benzene

Details on exposure:

TYPE OF INHALATION EXPOSURE: nose/head only

GENERATION OF TEST ATMOSPHERE / CHAMPER DESCRIPTION
Test product was vaporized by a generator. The exposure system was placed in a second gastight enclosure (glovebox).
The generator (based on the technique of Lauterbach, Hayes and Coelho; K.E. Lauterbach, A.B. Hayes anu M.A. Coelho: An improved aerosol generator, Archs. Ind. Health, 13, 156 (1956)), is designed to produce a vapor with droplets of reproducible particle size distribution. Its flow rate matches the normal respiratory rate of the animals. It utilizes a compressed dry air jet under high pressure and at low flow rate (1.4 bar through a hole 0.3 mm in diameter, giving a flow-rate of 3.5 L/min) flush with the surface of the liquid to be put in suspension. The equipment was adapted to obtain vapors rather than an aerosol.
The individual restraining cages containing the animals (a total of 12 rats) were placed in inhalation chamber (5 L). The rats were not anesthetized. The truncated-cone shape of the cephalic extremity of their restraining recipient and the small size of this recipient limited external contamination of the animal to its muzzle.
For each experiment one millicurie of TDI (14C) was used. The specific activity of this compound was 1 mCi/mM, which corresponds to a mass of 4.579 mg of 14C-TDI.
The concentration of 14C-TDI in the test atmosphere was calibrated with cold TDI.
The individual dose received by the animals were computed from the total radioactivity accumulated by each animal and assuming that 1 µg unconverted 14C-TDI corresponds to 485,000 desintegration/min. These doses ranged between 0.15 - 0.28 mg/kg bw.

Duration and frequency of treatment / exposure:

45 min

Doses / concentrations

Dose / conc.:

0.1 mg/L air

Remarks:

0.85 vpm (ppm by volume)

No. of animals per sex per dose / concentration:

12 (2 animals each were sacrificed 0.75, 24, 72, and 120 h after the end of the exposure period, 2 additional animals were used for bile secretion and sacrificed after 54 h and the remaining 2 were used for the autoradiography of the whole animals 45 min after the exposure)

Control animals:

yes, concurrent vehicle

Details on study design:

Preliminary study:
3 animals were exposed to half a millicurie for one hour.

Details on dosing and sampling:

METABOLITE CHARACTERISATION STUDIES
- Body fluids sampled: urine, feces, tissues, bile (catheter), whole blood (obtained by puncture of the abdominal aorta), plasma, ultrafiltrate of plasma, GI-tract content
- Time and frequency of sampling: urine/feces: 0 - 12, 12 - 24, 24 - 48, 48 - 72, 72 - 96, 96 - 120 h after administration of 14C-TDI
- Tissues sampled: brain, heart, stomach, liver, large intestine, small intestine, muscles, eyes, skin, lungs, spleen, kidneys, adrenals, testicles, thyroid
- Method types for identification:
Autoradiography: localization of radioactivity in the whole animal
Liquid scintillation counting: for determination of overall radioactivity
Histological tests with collagen stain: test for histological effects, lung samples only
Thin layer chromatography: separation of metabolites from urine, bile, feces, plasma and lungs; discrimination between polar and less polar metabolites.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

It was assumed that 10 % of the dose is absorbed.

Details on distribution in tissues:

- 45 min after exposure, autoradiographies showed a relatively uniform distribution throughout the organism, with predominance in the stomach, small intestine and kidneys (medullar zone) as detected by autoradiography. Only the lungs were labelled in a non-uniform manner. The radioactivity appeared to be localized at the bronchi.
- Liquid scintillation counting detected the largest amount of labeled TDI in the lungs, kidneys and thyroids.
- > 90 % of the 14C-TDI and its metabolites was associated with plasma proteins.

Details on excretion:

- Within 120 h 23.4 % of the total dose absorbed was excreted by urine and 63.1 % by feces. At that time 12.6 % remained in the carcass (see table 2).
- During the first 52 h ~8 % of the total dose absorbed was excreted via bile. Radioactivity peak in bile was between 6 - 9 h.
- The elimination of 14C-TDI from the blood follows a second order kinetic.
- Highest blood radioactivity on hour following exposure, after 5 days 86 % of the absorbed dose was eliminated (see table 1).

Toxicokinetic parameters

Key result

Toxicokinetic parameters:

half-life 1st: bile elimination = 25.5 h

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

Urine: polar and less polar metabolites are found. The proportion of polar derivates in the urine diminished with time, while that of less polar derivates increased. Six hours after treatment, the most abundant labelled derivate represented 25 - 30 % of the radioactivity in the urine.
Bile: 90 % of the metabolites were associated with strong polar compounds, 10 % were less polar compounds. The distribution of radioactivity did not change over time.
Plasma: the radioactivity was associated with albumin, no separation of metabolites could be obtained.
Ultrafiltrate: 4 labeled metabolites could be detected.
Lungs: extremely polar metabolites were detected.
Feces: separations were unsatisfactory but predominance of strongly polar radioactive derivatives was confirmed.

Samples were treated with beta-glucuronidase and sulfatase. A slight increase of strongly polar compounds in the urine, a slight decrease in strongly polar compounds in the bile and no changes of plasma metabolites were observed.

Any other information on results incl. tables

Histological tests performed on lung fragments revealed:

- lesions at the bronchi, bronchial and endothelial cells (considerable congestion of capillaries, infiltration of poly nuclears with mononuclear cells, specific destruction of the broncheal epithelium, exudate and desquamation).

- absence of pulmonary edema and lesions at the pulmonary epithelium.

A control experiment performed with benzene alone showed the same lesions as those observed with benzene and TDI after histological examination.

Table 1: 14C radioactivity-concentration in the blood, plasma and ultrafiltrated fraction of the plasma, in rats treated via the respiratory tract with 14C-TDI. The results were evaluated as a function of the total radioactivity received by each rat, calculated per gram of blood, plasma or ultrafiltrate

time [h]	numer of rats	median [% total 14C] blood	median [% total 14C] plasma	median [% total 14C] ultrafiltrate
0.75	2	2.5415	3.63095	0.5008
24	2	1.3259	4.2604	0.0246
72	2	0.4598	0.6281	0.0057
120	3	0.2776	0.3383	0.0034

Table 2: Mean (n=3) urinary and fecal elimination of 14C as a function of time, after respiratory exposure with 14C-TDI. The results are expressed in parts per 1000 of the dose administered. 0 equals absence of feces

collection period	mean in urine	mean in faeces	urine+faeces	carcass
0 -6	64.28 +/-12.47	7.42  +/-7.42
6 -12	48.55  +/-11.48	4.54  +/-4.54
12 -24	52.55  +/-19.93	245.88  +/-38.02
24 -48	36.61  +/-1.11	272.12  +/-39.87
48 -72	16.61  +/-1.19	56.68  +/-6.79
72 -96	11.7 +/-0.88	30.65  +/-4.92
96 -120	3.75  +/-1.13	13.55  +/-0.74
total	234.16  +/-22.08	630.63  +/-22.26	864.79 +/- 9.9	126.65 +/-12.4

Table 3: Mean radioactivity distribution in organs as fraction of total dose absorbed (x10^-3)

organ	0.75h (1 rat)	24h (5 rats)	72h (2 rats)	120h (2 rats)
brain	0.34	0.10	0.05	0.07
heart	0.85	0.39	0.16	0.14
GI-tract content	156.24	199.4	15.1	4.6
stomach	3.1	1.14	0.21	0.15
liver	10.26	5.41	2.1	1.14
large intestine	2.8	5.3	0.54	0.28
small intestine	13.9	2.7	0.6	0.9
muscles	48.8	26.91	13.1	7.8
eye	0.23	0.21	0.031	0.051
skin	21.4	12.03	6.12	4.34
lungs	11.9	6.34	5.96	1.3
spleen	0.41	0.25	0.11	0.09
kidneys	9.55	6.5	2.51	1.08
adrenals	0.025	0.02	0.008	0.006
testicles	1.04	0.96	0.39	0.21
thyroid	0.074	0.016	0.005	0.005
whole blood	64.9	33.44	11.62	-
plasma	51.28	29.32	6.26	-
ultrafiltrate	4.81	0.34	0.075	-