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Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Not reported
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Cross-reference
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
publication
Title:
Hydroxylation of lauramide diethanolamine by liver microsomes
Author:
Merdink J, deCosta K, Mathews JM, Jones CB, Okita JR and Okita RT
Year:
1996
Bibliographic source:
Drug Metab. Dispos. 24(2):180-186

Materials and methods

Objective of study:
metabolism
Principles of method if other than guideline:
Liver and kidney microsomes from DEHP-treated and control rats were incubated with 100 µM test substance for 30 min at 37°C in a shaking water bath. The metabolites were then separated and analysed by GC-MS. 
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Lauramide diethanolamine (LDEA)
- Lot/batch No.: Ch1E952
- Locations of the label (if radiolabelling): On the DEA moiety
- Other: Identification by mass spectrometry and proton NMR
Radiolabelling:
yes

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male

Administration / exposure

Details on exposure:
Diethyl hexyl pthalate (DEHP) and control treated liver and kidney microsomes were incubated with 100 µM of test substance for 30 min at 37°C in a shaking water bath according to the method of Okita et al, 1990 .
Duration and frequency of treatment / exposure:
30 min
Doses / concentrations
Dose / conc.:
100 other: µM
Details on dosing and sampling:
METABOLITE CHARACTERISATION STUDIES:
- Method of identification: Mass spectral identification (GC/MS).
- Because LDEA contains a 12-carbon side chain, LDEA hydroxylation rates were compared with the hydroxylation rates for lauric acid.




Results and discussion

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
The test substance was metabolised by rat liver microsomes to two major products that were identified by GC/MS to be the 11- hydroxyl and 12-hydroxy derivatives. The specific activities for 11- and 12-hydroxylation in microsomes prepared from control rats were 2.23±0.40 and 0.71±0.17 nmol/min/mg protein, respectively.

Treatment of rats with the cytochrome P4504A inducer and peroxisome proliferator, diethylhexyl phthalate (DEHP) increased the test substance 12-hydroxylation rate to 3.50 ± 0.48 nmol/mm/mg protein, a 5-fold increase in specific activity, whereas the 11-hydroxylase activity remained unchanged.

The specific activities of 11- and 12-hydroxylation reactions in DEHP treated rats were 1.7-fold and 3.2-fold greater than the 11- and 12-hydroxylation rates, respectively.

Incubating liver microsomes from DEHP-treated rats with a polyclonal anti-rat 4A inhibited the formation of 12-OH-test substance by 80% (3.98±0.10 vs. 0.80±0.08 nmol/min/mg protein), compared with the preimmune serum, but had no inhibitory effect on the rate of 1 1-OH-test substance formation (1.93±0.09 vs. 2.20± 0.11 nmol/min/mg protein).

Rat kidney microsomes also resulted in hydroxylation of the test substance at its 11- and 12-carbon atoms, with specific activities of 0.05±0.01 and 0.28±0.02 nmol/min/mg protein, respectively.

A 5.1-fold increase in specific activity was observed for the test substance l2-hydroxylation reaction after DEHP treatment, whereas the rate for 11-hydroxylation was similar in microsomes from control and DEHP-treated rats.

Any other information on results incl. tables

Other studies: Human liver microsome results: LDEA was also metabolised to 11- and 12-hydroxy derivatives by human liver microsomes at specific activities of 0.22±0.06 and 0.84±0.26 nmol/min/mg protein, respectively.

Applicant's summary and conclusion

Conclusions:
Under the study conditions, the test substance was rapidly converted into 11- and 12-hydroxy derivatives in rat liver and kidney microsomes.
Executive summary:

A study was conducted to evaluate the in vitro metabolism of N,N-bis(2-hydroxyethyl)dodecanamide (LDEA) in liver or kidney microsomes from rat to: 1) determine the extent of its hydroxylation, 2) identify the products formed and 3) examine whether treatment with the cytochrome P4504A inducer and peroxisome proliferator diethylhexyl phthalate(DEHP) would affect hydroxylation rates. Liver and kidney microsomes from DEHP-treated and control rats were incubated with 100 µM LDEA for 30 min at 37°C in a shaking water bath. The metabolites were then separated and analysed by GC-MS.  97% of the hydroxylated products were identified as two major substances: 11- hydroxyl and 12-hydroxy derivatives of LDEA. The specific activities for LDEA 11- and 12-hydroxylation in microsomes prepared from control rats were 2.23±0.40 and 0.71±0.17 nmol/min/mg protein, respectively. Treatment of rats with DEHP increased the LDEA 12-hydroxylation specific activity 5-fold to 3.50 ± 0.48 nmol/mm/mg protein, whereas the LDEA 11-hydroxylase activity remained unchanged. Incubating liver microsomes from DEHP-treated rats with a polyclonal anti-rat 4A inhibited the formation of 12-OH-LDEA by 80% (3.98±0.10 vs. 0.80±0.08 nmol/min/mg protein), compared with the pre-immune serum, but had no inhibitory effect on the rate of 1 1-OH-LDEA formation (1.93±0.09 vs. 2.20± 0.11 nmol/min/mg protein). Rat kidney microsomes also resulted in hydroxylation of LDEA at its 11- and 12-carbon atoms, with specific activities of 0.05±0.01 and 0.28±0.02 nmol/min/mg protein, respectively. In conclusion, under the study conditions, the test substance was rapidly converted into 11- and 12-hydroxy derivatives in rat liver and kidney microsomes (Merdink, 1996).