4,4'-methylenediphenyldiisocyanate and 2,4'-diisocyanatodiphenylmethane and their oligomerisation reaction products with 2,2'-oxydiethanol, propane-1,2-diol and butane-1,3-diol

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: Study meets generally accepted scientific principles

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Unnamed

Year:

1997

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Materials and methods

Objective of study:

distribution

excretion

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Principles of method if other than guideline:

Distribution and excretion of [14C]MDI after topical application for 24 and 48h.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

4,4'-methylenediphenyl diisocyanate

EC Number:

202-966-0

EC Name:

4,4'-methylenediphenyl diisocyanate

Cas Number:

101-68-8

Molecular formula:

C15H10N2O2

IUPAC Name:

1,1'-methylenebis(4-isocyanatobenzene)

Constituent 2

Reference substance name:

benzene, 1,1'- methylenebis[4-isocyanato-

IUPAC Name:

benzene, 1,1'- methylenebis[4-isocyanato-

Details on test material:

[Ring-U-14C]methylenediphenyl-4,4'-diiso-cyanate, [14C]MDI (Amersham)
specific activity 28 mCi/mmol
Acetone was dried 1 day before use by distillation over sodium sulphate and was added to the screwcapped vials containing [14C]MDI.
Quantitative analysis of isocyanate group content as ethylcarbamate by HPLC analysis.

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Ivanovas, Kisslegg, FRG or from BRL, Basel, Switzerland
- Weight at study initiation: approx. 220 g.
- Housing: Macrolone cages
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): NAFAG 890, Nafag AG, Gossau SG, Switzerland
- Water (e.g. ad libitum): yes
- Acclimation period: 7 days

Administration / exposure

Route of administration:

dermal

Vehicle:

acetone

Details on exposure:

TEST SITE
- Area of exposure: 3 x 3 cm
- Type of wrap if used: non, without occlusion
- Time intervals for shavings or clipplings: clipped 1 or 3 days prior to dosing.

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): approximately 100 µl, 2.5-3.6 mg MDI (experiment 1) or 6.9 mg MDI (experiment 2)

Doses / concentrations

Remarks:

Doses / Concentrations:
15.1 and 10.9 mg/kg bw (experiment 1) or 29.8 and 29.1 mg/kg bw MDI (experiment 2).

No. of animals per sex per dose / concentration:

4 in total

Control animals:

yes, concurrent vehicle

Details on dosing and sampling:

Animals were killed after 24h or 48h.
Blood was drawn by open heart puncture.
Epidermis (including hair remnants) of the treated area was scraped off with a scalpel blade.
The remainder of the skin, after removal of the subcutaneous fat, was analyzed as dermis.
Tissues and body fluids sampled: urine, faeces, blood, plasma, serum and organs.
In an additional experiment DNA and nuclear protein were isolated and the amount of [14C]MDI binding was determined. DNA binding was additionally assayed by the 32P-postlabeling method.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

24h (48h) after topical administration of radiolabeled MDI, about 10% (12%) of the radioactivity was still found in the treated epidermis.

Details on distribution in tissues:

Total recovery: 50%
Systemic distribution of radioactivity was more or less uniform (1 nmol MDI equivalent per g tissue).
Only in the tongue the radioactivity was higher (due to low amount of oral exposure).
Dermal concentration was about 50 times higher than in blood. Concentrations in the muscle were 10 times lower than in blood.
Plasma concentration of radioactivity was 1.8-fold higher than the concentration in whole blood.

Details on excretion:

In feces after 24h: 22 and 16%
In feces after 48h: 6 and 15%.
In urine after 24h: 0.6 and 0.8%
In urine after 48h: 0.2 and 0.3%
(for 2 rats each)

Metabolite characterisation studies

Details on metabolites:

In the same study protein and DNA associated radioactivity in the epididermis, dermis , lung, liver, and kidney was assayed.
Nuclear protein exhibited extremely high specific activities (up to 10exp6 dpm/mg) in the epidermis. Specific activities of nuclear protein from liver, lung and kidney were about 10000-fold lower.
In experiment 1 (24h, 350µCi [14C]MDI administered per rat) none of the DNA samples contained detectable radioactivity.
In experiment 2 (48h, double amount of MDI-radioactivity) some hardly detectable radioactivity was associated with the DNA of both epidermis and liver (3-4 adducts per 10exp7 DNA-nucleotides.) But this includes the metabolites and conjugates which were systemically available.
In view of the extremely high radioactivity associated with epidermal protein, a substantial fraction of the DNA radioactivity is expected to be due to contamination by protein.
Conversion to the units of the Covalent Binding Index, CBI = (μmol adduct/mol DNA nucleotide per mmol chemical administered/kg bw) resulted in a value of <0.1 (maximum binding).
32P-postlabeling analysis did not reveal isocyanate-DNA adducts.

Any other information on results incl. tables

Table 1: Distribution of radioactivity after topical application of [14C]MDI, 24 and 48 h postdosage.

	experiment 1 (24h)		experiment 2 (48h)
body weight	242	235	232	238
dose (mg/kg)	15.1	10.9	29.8	29.1
dose (nmol/g)	60	43	117	114
epidermis (nmol/g)	2200 (9)	1700 (12)	9300 (12.6)	13000 (12)
dermis (nmol/g)	n.d.	n.d.	74 (0.2)	127 (0.4)
blood (nmol/ml)	1.4 (0.16)	0.6 (0.1)	1.3 (0.08)	2.2 (0.14)
plasma (nmol/ml)	n.d.	n.d.	2.4	4.2
tongue (nmol/g)	5.1 (0.017)	1.2 (0.007)	n.d.	n.d.
lung (nmol/g)	0.6 (0.004)	0.4 (0.005)	0.6 (0.002)	1.1 (0.005)
liver (nmol/g)	1.7 (0.09)	1.4 (0.09)	1.8 (0.05)	3 (0.09)
kidney (nmol/g)	1 (0.019)	0.8 (0.012)	1.8 (0.011)	2.9 (0.017)
muscle (nmol/g)	n.d.	n.d.	0.2 (0.064)	0.3 (0.067)
feces 24h (nmol/g)	n.d.	n.d.	1985 (22.5)	1470 (16.3)
feces 48h (nmol/g)	n.d.	n.d.	1211 (6)	1777 (14.6)
urine 24h (nmol/ml)	n.d.	n.d.	27 (0.56)	26 (0.81)
urine 48h (nmol/ml)	n.d.	n.d.	10 (0.2)	6 (0.34)

In brackets: percentage of radioactivity in whole organ in relation to the total administered

n.d., not determined.