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Diss Factsheets

Administrative data

additional toxicological information
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication which meets basic scientific principles.

Data source

Reference Type:
The Incorporation of Monomethylethanolamine and Dimethylethanolamine in Fetal Brain Aggregating Cell Culture
Dainous, F. and Kanfer, J.N.
Bibliographic source:
Neurochemical Research, Vol. 13, No. i, 1988, pp. 1-8.

Materials and methods

Type of study / information:
Test guideline
no guideline followed
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Details on test material:
[3H] dimethylethanolamine (DME)(24.9 x 10^6 cpm/µmol) was obtained from Aldrich Chemical Co. (Milwaukee, Wisc.)
Phosphatidylethanolamine,phosphatidyl-N-monomethylethanolamine (PMME), phosphatidylcholine (PC), sphingomyelin, lysophosphatidylcholine, CDP-MME and phosphoryl-MME (Ph-MME) chemically synthesized were used as standards to visualize the exposure.

Results and discussion

Any other information on results incl. tables

1. Time-course of [3H]MMEA incorporation into phospholipids and water-soluble products.

Fetal rat brain aggregating cultures were grown in medium containing labeled MMEA for different time intervals and the radioactivity incorporated into the lipids plateaued at about 48 hours.

a) The principal labeled phospholipid was phosphatidylmonomethylethanolamine (PMMEA) which contained more than 80% of the total lipid bound radioactivity. Little label was associated with either phosphatidyldimethylethanolamine (PDMAE) or phosphatidylcholine (PC).

b) The magnitude of radioactivity present in the total water-solubles was considerably greater than that present in lipids and a plateau was reached by 24 hours. The majority of the radioactivity was present in a material chromatogramming like phosphorylmonomethylethanolamine (Ph- MMEA). There was less radioactivity associated with MMEA and the presumed CDP-monomethylethanolamine (CDP-MMEA).

2. Effect of Varying the Concentrations of [3H]DMAE on the Labeling of Water- Solubles and Phospholipids.

The amount of radioactivity present in products in the presence of varying concentrations of [3H]MMEA was estimated after an 8 hour incubation. The amount of radioactivity present in PMMEA and Ph-MMEA continued to increase up to 4 mM [3H]MMEA, the highest concentration employed. The quantity of radioactivity in PDMAE and PC (Figure 3A) was slight at 4 mM MMEA suggesting that N-methyltransferase activity is relatively inactive under these conditions. There was a slight increase of the labeling of MMEA and CDP-MMEA with increasing base content in the medium.

3. Effect of Various Growth Media on MME and DME Incorporation.

Growth media:

a) Control = cells grown and incubated in DMEM (Dulbecco's Modified Eagle Medium).

b) Met = cells grown and incubated in DMEM in L-methionine free medium

c) Ch = cells grown and incubated in DMEM in choline free medium.

After labeling with [3H]MMEA for 24 hours, 25% of the isotope was recovered in lipids (Table I) and most was present in PMMEA. In cells grown in medium devoid of choline, the labeling of lipids and PMMEA was 145% and 150% respectively as compared to control values. There was no significant differences in labeling in cells grown in medium devoid methionine as compared to controls. The conversion of PMMEA to PDMAE or PDMAE to PC was very low in the three growth medium. The radioactivity associated with MMEA and Ph- MMEA was reduced in cells grown in the absence of methionine, after 1 day the radioactive medium was removed and replaced by DMEM medium containing non-radioactive MMEA and this resulted in a rapid decline in the radioactivity present in MMEA and Ph-MMEA by 2 days. The decrease was less pronounced with the phospholipids and at 2 days, PMMEA was still the major product.

Applicant's summary and conclusion

Dimethylaminoethanol was rapidly phosphorilated after it entered the cell and served as a precursor of phosphatidyldimethylethanolamine. The rate of incorporation of DMAE into phospholipids was slower than the incorporation into water-soluble products.
Executive summary:

Fetal rat brain aggregating cell cultures were exposed to varying concentrations of [3H]monomethylethanolamine (MMEA) and [3H] dimethylethanolamine (DMAE). The rate of labeling of water-soluble compounds was more rapid and the amount of radioactivity present was greater than in the lipids. After a 72 hour incubation in the presence of millimolar concentrations of these nitrogenous bases, the major water-soluble products were the phosphorylated form of the bases. Little label was associated with the free bases or their cytidyl derivate. In the phospholipids, 97% of the radioactivity was recovered in phosphatidylmonomethylethanolamine (PMMEA) and 3% in phosphatidyldimethylethanolamine (PDMAE) or 95% in PDMAE and 5% in phosphatidylcholine (PC) after growth in presence of [3H]MMEA and [3H]DMAE, respectively. The rate of formation of the radioactive products increased as function of the concentration of the nitrogenous base added up to 4 mM, the highest concentration employed. There was no significant difference in the pattern of labeling with cells grown in media devoid of methionine or choline. The turnover of the water-soluble metabolites was more rapid than in the phospholipids where an apparent half-life of 24 hours was calculated.