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Toxicological information

Dermal absorption

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Administrative data

Endpoint:
dermal absorption in vivo
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: reliable without restriction

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1999
Report Date:
1999

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
EPA OPPTS 870.7600 (Dermal Penetration)
Principles of method if other than guideline:
Absorption, distribution and excretion of radioactivity was studied in male Wistar rats following a single dermal and intradermal administration of [14C]-MDI.
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
14C-labelled material:
- Name of test material: 14C-Methylenebisphenylisocyanate
- Physical state: solid
- Radiochemical purity: >95 % as determined by HPLC analysis
- Lot/batch No.: 588-02 and 588-1201
- Specific activity (if radiolabelling): 2140624 dpm/mg
- Locations of the label (if radiolabelling): 4,4´-Methylenebis-[ring-U-14C]-phenylisocyanate

unlabelled material:
- Name of test material: 4,4´-Methylenebisphenylisocyanate, Lupranat ME
- Physical state: solid
- Radiochemical purity: >95 % as determined by HPLC analysis
- Lot/batch No.: 152.08.16.95

Stock solutions were prepared in dried acetone. For intradermal administration corn oil was used as a carrier. Stability and homogeneity were analysed before start of and at the end of the administrations.
Radiolabelling:
yes

Test animals

Species:
rat
Strain:
Wistar
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Dr. Karl Thomae, Biberach (FRG)
- Age at study initiation: 8 weeks
- Weight at study initiation: ca. 250-300 g
- Housing: type III Macrolon cages
- Individual metabolism cages: yes, type Metabowl
- Diet (e.g. ad libitum): Kliba lab diet (Klingentalmühle AG, CH-4303, Kaiseraugst, Switzerland)
- Water (e.g. ad libitum): yes


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24°C
- Humidity (%): 30-70% relative

Administration / exposure

Type of coverage:
semiocclusive
Vehicle:
acetone
Duration of exposure:
8h
Doses:
dermal administration: 4 and 0.4 mg/cm2 corrsponding to 40 and 4 mg/animal (approx. 140 and 14 mg/kg bw)
intradermal administration: 0.4 mg/animal (1.4 mg/kg bw)
No. of animals per group:
4 dose and exposure group
Control animals:
no
Details on study design:
Dermal administration:
24 h prior to dosing the back shoulders of the rats were clipped free of hair and the area (about 10 cm2) was washed with acetone.
A silicon ring was glued to the skin, the test substance preparation (about 10 µl/cm2) was administered with a syringe which was weighed before and after application. A nylon mesh gauze was then glued to the surface of the silicone ring and a porous bandage used to encircle the trunk of the animal.
Duration of exposure: 8h

Intradermal administration:
24h prior to dosing the back shoulders of the rats were clipped free of hair and the area (about 10 cm2) was washed with acetone. The test substance preparation (about 100 µl) was administered with a syringe which was weighed before and after application . The injection area was sealed with tissue glue in order to avoid leakage of the test substance preparation.

Pretest for intradermal administration:
Using unlabelled test substance in two male rats with intradermal administration of 0.4 mg MDI/animal.

Collection of excreta: after 8, 24, 48, 72, 96 and 120 h if animals were not sacrificed before.
Sacrifice after 8, 24, 120h
After the respective exposure period the protective cover was removed and the exposed skin was washed with a mild soap solution.
At the end of the various collection periods animals were sacrificed and the following specimens/tissues were analysed for remaining radioactivity:
excreta, bloodcells, plasma, lung, heart, spleen, kidneys, adrenals, gonads, muscle, brain, adipose tissue, bone, thyroid, pancreas, stomach contents, stomach, gut contents, gut, liver, carcass, skin (treated and non-treated areas).
Additionally cage wash, skin wash and the protective cover (including the silicone ring) were also analysed for radioactivity.

For immunological investigations, retroorbital sampling of blood was performed after dermal and intradermal administration of non-radioactive MDI (results reported elsewere).

Radioactivity was measured by liquid scintillation counting.

Results and discussion

Signs and symptoms of toxicity:
no effects
Absorption in different matrices:
Absorption: Very limited absorption after dermal administration (0.9%) but considerable absorption after intradermal administration (26%). Due to the reactive nature of the test substance, considerable amounts of radioactivity could be found at the application site which could not be washed off .
Percutaneous absorption
Remarks on result:
other:

Any other information on results incl. tables

The test substance was stable in the respective carriers.

Excretion, retention and tissue concentrations after dermal application of 14C-MDI:

Table 1: Mean excretion and retention of radioactivity after a single dermal administration of 14C-MDI (% of the radioactivity administered).

nominal dose [mg/cm2]

4

0.4

sacrifice time [h]

8

24

120

8

24

120

actual dose [mg/cm2]

4.6

4.7

4.8

0.42

0.42

0.42

urine

0.01

0.03

0.05

0.01

0.04

0.09

feces

0

0.02

0.13

0

0.05

0.16

cage wash

0

0

0.03

0

0.01

0.06

stomach content

0

0

0.18

n.d.

n.d.

n.d.

gut content

0.02

0.02

0.29

n.d.

n.d.

n.d.

gut

0

0

0.01

n.d.

n.d.

n.d.

carcass

0.17

0.6

0.21

0.13

0.13

0.38

material absorbed

0.21

0.66

0.88

0.14

0.23

0.69

skin (surrounding)

4.75

7.14

0.55

3.17

1.37

1.47

protective cover

65.9

64.3

69.2

44.49

50.03

42.64

skin (application site)

29.6

25.5

32.2

54.26

55.62

61.14

skin wash

0.5

0.3

0.3

0.81

0.82

0.47

Total recovery

101

97.9

103.1

102.9

108.1

106.4

absorbtion [mg/animal]

0.0973

0.03165

0.4299

0.0058

0.0096

0.029

absorbtion [mg/cm2]

0.0097

0.0316

0.043

0.00058

0.00096

0.0029

In all groups, the largest proportion of radioactivity was recovered from the dressing and the skin of the application site. The amount of radioactivity absorbed (including excreta, cage wash, tissues/organs and carcass) increased in time, but remained below 1% at all dose levels. Excretion occured via urine and feces. In similar amounts after 8 and 24h, but to a higher extend in feces after 120h. The radioactivity absorbed was distributed in all organs and tissues. Due to the limited dermal absorption, concentrations of radioactivity in organs and tissues analyzed were considerably below 1 µg Eq/g (except for carcass). Levels of tissue radioactivity were comparable at 8 and 24 h and declined until 120 h after application with highest levels generally being found in carcass, thyroid, muscle, plasma and liver (not shown in table).

Excretion, retention and tissue concentrations after intradermal application of 14C-MDI:

Table 2: Mean excretion and retention of radioactivity after a single intradermal administration of 14C-MDI (% of the radioactivity administered).

nominal dose [mg/cm2]

0.4

sacrifice time [h]

120

actual dose [mg/cm2]

0.515

urine

4.51

feces

17.1

cage wash

0.75

stomach content

0.05

gut content

0.48

gut

0.09

liver

0.32

carcass

2.18

material absorbed

25.87

skin (surrounding)

8.47

skin (application site)

66.45

skin wash

0.11

Total recovery

100.9

absorbtion [mg/animal]

0.1332

The largest proportion of radioactivity was found at the application site. The amount of radioactivity absorbed (including excreta, cage wash, tissues/organs and carcass) during the 120 h observation period amounted to 25.87 % of the dose applied. Excretion occurred mainly via the feces and concentrations of radioactivity in organs and tissues were rather low being below 1 µg Eq/g.

Applicant's summary and conclusion