Registration Dossier

Administrative data

Endpoint:
hepatotoxicity
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
7 February 1989 - 7 March 1989
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study was not conducted according to a guideline, but perfomed under GLP, and acceptable basic data are given.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1990
Report Date:
1990

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
To investigate the ability of 2-ethylhexyl diphenyl phosphate (2EHDPP) to cause peroxisome proliferation in the rat liver when administered in the diet, 2EHDPP was fed to groups of 5 male Fischer 344 rats at dietary levels of 0 (control), 0.1, 0.3 or 0.6%, and to groups of 6 male Sprague-Dawley rats at levels of 0 (control), 0.3 or 1.2% for 28 days. A further group of 5 F344 rats were fed 1.2% di-(2-ethylhexyl)phthalate (DEHP) for 28 days and 4 Sprague-Dawley rats were fed 1.2% DEHP for 14 days to act as positive study controls. Observations were made for variations in behavior or condition, and weight changes. At necropsy liver weight, liver biochemistry (protein, cyanide-insensitive palmitoyl Co-A) and serum analysis (triglycerides and total cholesterol) were performed.
GLP compliance:
yes
Type of method:
in vivo

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 2-ethylhexyl diphenyl phosphate, 50/50 mixture of Santicizer 141 and Disflamoll
- Physical state: Liquid
- Storage condition of test material: Polypropylene container at room temperature

Test animals

Species:
rat
Strain:
other: Fischer 344 and Sprague-Dawley
Sex:
male

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Analytical verification of doses or concentrations:
yes
Duration of treatment / exposure:
28 days
Frequency of treatment:
Continuous (diet)
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
0.1, 0.3, and 0.6 % 2EHDPP
Basis:
nominal in diet
Male F344: 136, 401, and 765 mg/kg bw/day resp.
Remarks:
Doses / Concentrations:
0.3 and 1.2 % 2EHDPP
Basis:
nominal in diet
Male Sprague-Dawley: 404 and 1610 mg/kg bw/day resp.
No. of animals per sex per dose:
5 male Fischer 344/dose, and 6 male Sprague-Dawley/dose
Control animals:
yes, plain diet

Results and discussion

Details on results:
F344 rats given 0.3 and 0.6% EHDP, and Sprague-Dawley rats given 0.3 and 1,2% EHDP were lighter than their concurrent controls, and these animals all showed reduced food intake values initially, with the intake of those given 0.6 and 1.2% remaining low throughout the study. This latter effect was explained as a probable reaction to the unpalatability of the diet containing the test article.
There was a dose-related increase in both absolute and relative liver weight in both strains of rat given EHDP, but the livers showed no associated histological changes.
There were dose-related increases in serum triglyceride levels in all rats given EHDP, and F344 rats given 0.6% and Sprague-Dawley rats given 0.3 or 1,2% EHDP also showed increases in serum cholesterol levels. These changes are not associated with a peroxisome proliferator.
There were very small increases in specific palmitoyl-CoA oxidation activity (i.e. activity per mg protein) among F344 rats given 0.3 and 0.6% EHDP to 135 and 150% of control activities, resp. However, when the values were expressed per gram of liver (calculated independently of liver whole homogenate protein content), a significant increase was only observed at the 0.6% EHDP dose-level. There were no significant increases in palmitoyl-CoA oxidation activity among the Sprague-Dawley rats given EHDP.
Small decreases in hepatic whole homogenate protein content were observed in F344 rats given 0.3% EHDP and in Sprague-Dawley rats given 1.2% EHDP to 91.5% and 92.2% of the corresponding control values, resp. With both strains the small changes observed are unlikely to have any biological significance.

Any other information on results incl. tables

All the diets had a concentration of test article within the 10% range of nominal. Diets were stable for 28 days.

Applicant's summary and conclusion

Conclusions:
This study, investigating the ability of 2-ethylhexyl diphenyl phosphate (2EHDPP) to cause peroxisome proliferation in the rat liver when administered in the diet, could not identify a NOAEL level of 2EHDPP in terms of liver enlargement. The NOAELs for the induction of hepatic palmitoyl-CoA oxidation activity by 2EHDPP (as an index of peroxisome proliferation) were 1.2% in the diet of Sprague-Dawley rats (approx. intake of 1600 mg/kg/day) and 0.3% in the diet of Fischer 344 rats (approx. intake of 400 mg/kg/day). However, these figures were based upon only very minor changes in enzyme activities which probably have little, if any, biological significance. It is therefore thought unlikely that 2EHDPP produces peroxisome proliferation in the rat liver.
Executive summary:

To investigate the ability of 2-ethylhexyl diphenyl phosphate (2EHDPP) to cause peroxisome proliferation in the rat liver when administered in the diet, 2EHDPP was fed to groups of 5 male Fischer 344 rats at dietary levels of 0 (control), 0.1, 0.3 or 0.6%, and to groups of 6 male Sprague-Dawley rats at levels of 0 (control), 0.3 or 1.2% for 28 days. A further group of 5 F344 rats were fed 1.2% di-(2-ethylhexyl)phthalate (DEHP) for 28 days and 4 Sprague-Dawley rats were fed 1.2% DEHP for 14 days to act as positive study controls. Observations were made for variations in behaviour or condition, and weight changes. At necropsy liver weight, liver biochemistry (protein, cyanide-insensitive palmitoyl Co-A) and serum analysis (triglycerides and total cholesterol) were performed. The effect of 2EHDPP on hepatic peroxisomes was quantified by measurement of palmitoyl Co-A oxidation.

F344 rats given 0.3 and 0.6% 2EHDPP, and Sprague-Dawley rats given 0.3 and 1,2% 2EHDPP were lighter than their concurrent controls, and these animals all showed reduced food intake values initially, with the intake of those given 0.6 and 1.2% remaining low throughout the study. This latter effect was explained as a probable reaction to the unpalatability of the diet containing the test article.

There was a dose-related increase in both absolute and relative liver weight in both strains of rat given 2EHDPP, but the livers showed no associated histological changes.

There were dose-related increases in serum triglyceride levels in all rats given 2EHDPP, and F344 rats given 0.6% and Sprague-Dawley rats given 0.3 or 1,2% 2EHDPP also showed increases in serum cholesterol levels. These changes are not associated with a peroxisome proliferator.

There were very small increases in specific palmitoyl-CoA oxidation activity (i.e. activity per mg protein) among F344 rats given 0.3 and 0.6% 2EHDPP to 135 and 150% of control activities, resp. However, when the values were expressed per gram of liver (calculated independently of liver whole homogenate protein content), a significant increase was only observed at the 0.6% 2EHDPP dose-level. There were no significant increases in palmitoyl-CoA oxidation activity among the Sprague-Dawley rats given 2EHDPP.

Small decreases in hepatic whole homogenate protein content were observed in F344 rats given 0.3% 2EHDPP and in Sprague-Dawley rats given 1.2% 2EHDPP to 91.5% and 92.2% of the corresponding control values, resp. With both strains the small changes observed are unlikely to have any biological significance.

Based on these results it is therefore thought unlikely that 2EHDPP produces peroxisome proliferation in the rat liver.