2-amino-2-(hydroxymethyl)propane-1,3-diol hydrochloride

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

Percutaneous absorption of TRIS HCl was studied in 0.1% and 10% solution in-vitro in 4 samples of human abdominal skin, in a FRANZ diffusion cell.

GLP compliance:

not specified

Radiolabelling:

yes

Remarks:

carbon-14 labelled solution

Species:

other: in-vitro, human abdominal skin in a FRANZ diffusion cell

Strain:

other: in-vitro, human abdominal skin in a FRANZ diffusion cell

Sex:

not specified

Type of coverage:

other: not applicable

Vehicle:

not specified

Doses:

- Concentration: 0.1% (1 g/L) and 10% (100 g/L)
- Dose volume: 100 µL

No. of animals per group:

not applicable

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: human skin comes from biopsies obtained after plastic surgery of the abdomen
- Type of skin: human abdominal skin
- Preparative technique: skin is cut with a dermatome
- Thickness of skin (in mm): 0.3
- Storage conditions: stored frozen

PRINCIPLES OF ASSAY
- Diffusion cell: FRANZ diffusion cell
- Flow-through system: jacket with double circulation of water surrounds the lower part
- Test temperature: 37 °C

Key result

Time point:

24 h

Dose:

100 µl of a 10 % solution

Parameter:

percentage

Absorption:

< 1 %

Key result

Time point:

24 h

Dose:

100 µl of a 1 % solution

Parameter:

percentage

Absorption:

< 1 %

After 24 h, the percutaneous absorption of TRIS-HCl through human abdominal skin in-vitro was very low, regardless of the concentration of the solution. The mean percentages of the applied TRIS HCl dose that had passed into the survival liquid were 0.506 ± 0.765% for the 0.1% solution and 0.797 ± 0.691% for the 10% solution. These differences are not significant.

For both solutions, the maximum value of flux was reached after 4 h and remained essentially constant during the rest of the experiment. However, the value of flux was about 150 times higher for the 10% solution (6.922 ± 6.179 µg/cm2/h) than for the 0.1% solution (0.039 ± 0.052 µg/cm2/h).

After washing, the retention of the test substance in the epidermis and dermis was low: For the 0.1% solution, 0.14 ± 0.19% TRIS HCl remained in the epidermis and 0.69 ± 1.33% in the dermis. For the 10% solution, 0.13 ± 0.21% TRIS HCl was detected in the epidermis and 0.22 ± 0.21% in the dermis. Therefore, the test substance is not retained in the horny layer (epidermis).

The test substance was almost totally eliminated by washing the skin after 24 h. For the 0.1% solution, 91.13 ± 4.67% TRIS HCl was found in the washing waters and for the 10% solution, a quantity of 90.45 ± 4.06%.

However, significant differences in permeability from one skin sample to the other were recorded. (The experiments were carried out on 4 skin samples of different origin: mulatto skin; skin 2 and 3: white skin.) The differences of the individual measurements of the skin samples were lower for the 0.1% solution.

At the end of the 24 h, regardless of the concentration of the solution, the radioactivity found in the epidermis and the dermis was low (less than 1% of the applied dose) and the washing waters contained more than 90% of the applied dose.

Description of key information

percutaneous absorption in-vitro (human abdominal skin placed in a FRANZ diffusion cell): < 1%

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - dermal (%):

1

Additional information

A quantitative study of percutaneous absorption in-vitro was carried out on human abdominal skin placed in a FRANZ diffusion cell (reference 7.1.2 -1). After 24 h, the percutaneous absorption of TRIS HCl through human skin was very low regardless of the concentration of the TRIS HCl solution (10% and 0.1% TRIS AMINO solutions were tested). Less than 1% of the applied dose was found. For both solutions, the maximum value of flux was reached after 4 h and remained essentially constant during the rest of the experiment (totally 24 h). However, the value of flux was about 150 times higher for the 10% solution (6.922 ± 6.179 µg/cm²/h) than for the 0.1% solution (0.039 ± 0.052 µg/cm²/h). After washing, the retention of TRIS HCl in the epidermis and dermis was also less than 1% of the applied dose. Therefore, TRIS HCl did not retain in the horny layer but was almost totally eliminated by washing the skin. The washing waters contained more than 90% of the applied dose.