Isooctadecanoic acid, mono- and diesters with glycerol

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

11 Jul 2003 - 19 Jan 2004

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

GLP - Guideline study. According to the ECHA guidance document "Practical guide 6: How to report read-across and categories (March 2010)", the reliability was changed from RL1 to RL2 to reflect the fact that this study was conducted on a read-across substance.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2004

Report date:

2004

Materials and methods

Objective of study:

toxicokinetics

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Deviations:

yes

Remarks:

metabolism of the test substance was not evaluated

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

736150-63-3

EC Number:

616-005-1

Cas Number:

736150-63-3

IUPAC Name:

736150-63-3

Details on test material:

- Name of test material (as cited in study report): only trade name given
- Chemical name: 12-1-C14-acetoxy-octadecanoic acid-2,3-diacetoxypropyl ester
- Substance type: clear liquid
- Analytical purity: 85.6%
- Lot/batch No.: 10102
- Expiration date of the lot/batch: 22.11.2003
- Item No.: 175540
- Radiochemical purity (if radiolabelling): 96.7%
- Specific activity (if radiolabelling): 1.016 mCi/g (37.6 MBq/g) (calculated)
- Expiration date of radiochemical substance (if radiolabelling): 01.08.2004
- Lot/batch No.: 2329/51
- Storage condition of test material: at room temperature, light (out of direct light)

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

other: Sprague-Dawley Crl:CD (SD) BR

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Canada Inc., Quebec, Canada
- Age at study initiation: approx. 7 - 10 weeks
- Weight at study initiation: 260 - 362 g
- Housing: individually in stainless steel wire meshbottomed cages equipped with an automatic watering valve
- Individual metabolism cages: yes, for the high-dose group animals (test group 4)
- Diet: certified commercial laboratory diet (Harlan Teklad #8728CM), ad libitum (except during designated procedures)
- Water: municipal tap water, filtered through a 5 µm bacteriostatic polycarbonate filter, ad libitum (except during designated procedures)
- Acclimation period: approx. 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 50 ± 20 (the relative humidity was slightly higher than 70% on some occasions)
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on exposure:

UNLABELLED TEST ITEM: administered directly to the animals

LABELLED TEST ITEM: added to the unlabelled test item to achieve a target radioactivity level of 10 µCi/animal of 14C-test article at a target dose of 500 mg/kg bw (dose volume: 0.5 mL/kg) and 5000 mg/kg bw (dose volume: 5 mL/kg)

Duration and frequency of treatment / exposure:

UNLABELLED TEST ITEM:
test group 2 and 3: 12 days, once daily
test group 4: 8 days, once daily

LABELLED TEST ITEM:
test group 2, 3 and 4: single application on day 6

Doses / concentrations

Remarks:

Doses / Concentrations:
500, 5000 mg/kg bw day (0.5 or 5 mL/kg bw, respectively)

No. of animals per sex per dose / concentration:

1 (control), 24 (group 2 and 3), 5 (group 4)

Control animals:

yes, concurrent no treatment

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
TEST ANIMALS FROM GROUP 2 AND 3
- Tissues and body fluids sampled: blood, adipose tissue (perirenal), gastrointestinal tract and contents, kidneys, adrenals, liver and thymus
- Time and frequency of sampling: 1, 3, 6, 12, 24, 48, 72 and 168 h post labelled dose exposure
- Other: number of analysed animals/time point: 3
Remaining carcasses were collected from animals killed at 12, 24, 48 and 72 h only. All other remaining carcasses were discarded.


METABOLITE CHARACTERISATION STUDIES (test animals from group 4):
- Tissues and body fluids sampled: urine, faeces, cage washes (after 72 h post labelled dose exposure)
- Time and frequency of sampling: 6, 12, 24, 48 and 72 h post labelled dose exposure
- From how many animals: 5
- Other:
Expired 14CO2 was collected by drawing the cage air through a single collection tower (containing ca. 300 mL 4N KOH, target flow rate: 500-600 mL/min). Moisture and CO2 were removed from the air drawn through the cage by columns of anhydrous calcium chloride (Drierite) and Ascarite, respectively.
- Time and frequency of sampling: 3, 6, 12, 24, 48 and 72 h post radiolabelled dose.

Statistics:

Group mean values and standard errors were calculated from the examined parameters.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

For groups 2 and 3, the highest radioactivity concentration in the tissues analyzed was observed at 1 h post treatment in the gastrointestinal tract and contents and then decreased over the 168 h period post dose. From the 48 h time point, the liver, the kidneys and adrenals and the thymus showed higher radioactivity concentrations than the gastrointestinal tract and contents in both groups. Thus, absorption of the test arcticle in the systemic circulation is present.
The radioactivity concentrations in adipose tissue (perirenal fat) increased from the 24 h time point throughout the study in group 2 and from the 12 h time point to the 72 h time point in group 3.

Details on distribution in tissues:

RADIOACTIVITY IN BLOOD AND PLASMA
500 mg/kg bw: blood and plasma radioactivity concentrations revealed their maximum 1 h post administration and decreased rapidly over the course of the study (1h: 106.1 µg eq/mL and 138.1 µg eq/mL; 168h: 15.2 µg eq/mL and 5.3 µg eq/mL for blood and plasma levels, respectively)
5000 mg/kg bw: blood and plasma radioactivity concentrations reached their maximum concentrations 6 h post treatment and decreased slowly (1h: 253.4 µg eq/mL and 300.7 µg eq/mL; 6h: 434.0 µg eq/mL and 672.4 µg eq/mL; 168h: 118.6 µg eq/mL and 40.5 µg eq/mL for blood and plasma levels, respectively)
Blood to plasma ratios in group 2 and group 3 animals were similar and lower than 1 (0.6 to 0.8) up to 24 h post administration indicating that little radioactivity was associated with blood cells. Further, less than 1.5% of the dose was found in the blood for animals of both test groups.

RADIOACTIVITY IN TISSUES AND GASTROINTESTINAL TRACT
low- and high-dose group: the highest radioactivity concentration in the tissues analysed was observed at 1 h post treatment in the gastrointestinal tract (approx. 2922 µg eq/g and 44050 µg eq/g for group 2 and group 3, respectively). These levels decreased over the course of the study to 12 µg eq/g and 122 µg eq/g for group 2 and 3 animals, respectively, representing both excretion of the test article from the gastrointestinal tract and absorption of the test article into the systemic circulation.
From the 48 h time point, the liver, the kidneys, adrenals and the thymus showed higher radioactivity concentrations than the gastrointestinal tract in both groups. For group 2 animals, the radioactivity concentrations in these tissues gradually declined over the 168 h period post-dose. For group 3 animals, the kidneys and adrenals, thymus and liver reached maximum concentrations at the 6, 12 and 24 h time point, respectively, and then declined for the rest of the observation period. The radioactivity concentrations in adipose tissue (perirenal fat) increased from the 24 h time point throughout the study in group 2 and from the 12 h time point to the 72 h time point in group 3. The radioactivity concentrations in adipose tissue (perirenal fat) then decreased until the 168 h time point for group 3 animals (at this time point, the radioactivity concentration in adipose tissue (perirenal fat) for 2 animals from group 3 could not be reported since the values measured were inconsistent and could not be reproduced). The highest tissue to plasma ratio was observed at 1 h post treatment in the gastrointestinal tract and contents at approximately 23 and 152 for group 2 and 3 animals, respectively. Due to excretion of the test article from the gastrointestinal tract, this ratio decreased rapidly over the course of the study to 2.4 for both groups at 168 h post dose. For kidneys and adrenals, the tissue to plasma ratio decreased from the 3 h time point to the 12 h time point in both groups. For most other tissues in both groups, the tissue to plasma ratios increased during the course of the study indicating a faster clearance from plasma than tissues. The lowest tissue to plasma ratios were observed in the adipose tissue (perirenal fat) of both groups.
The highest percentage of dose in tissues was observed in the gastrointestinal tract and contents at 1 h post dose for group 2 at approximately 50% and at 3 h post dose for group 3 at approximately 81% as expected since the test article was administered by gavage. Due to excretion and absorption of the test article, the percent of dose in the gastrointestinal tract decreased rapidly over the course of the study to 0.2% and 0.3% for group 2 and 3 animals, respectively, at 168 h post dose. The percent of dose in the carcasses was similar and constant for both groups at the selected time points (12 h, 24 h, 48 h and 72 h post administration) indicating that the test article may have been distributed in other tissues than the ones selected for analyses. Group 2 values ranged from 8.3% to 4.9% and group 3 values ranged from 7.2% to 5.4%. For group 2, the percentage of dose in the liver was 2.5% at 1 h post dose and decreased throughout the study to 0.2%. The percentage of dose in all other tissues for both groups was less than 1.5%. The lowest percentage of dose was found in the adipose tissue (less than 0.018%).

Details on excretion:

CLEARANCE FROM BLOOD vs PLASMA:
The blood to plasma ratio in test group 2 and 3 increased over the study period starting 48 h after substance administration. Thus, a faster clearance from the plasma than from blood is indicated.

CLEARANCE FROM TISSUE vs PLASMA:
For most tissues, the tissue to plasma ratios increased during the course of the study indicating a faster clearance from plasma than tissues.

EXCRETION AND MASS BALANCE
5000 mg/kg bw (group 4): the mean total recovery of radioactivity in the excreta of the 72 h period post dose was 108.5% of the dose (urine, 6.5%; feces, 24.6%; CO2, 77%; and cage wash, 0.5%). Most of the recovered radioactivity (97.5%) was excreted by 24 h post dose. The data demonstrated that the greatest amount of radioactivity was eliminated via the expired air, with some excretion via the feces. Little radioactivity was eliminated via the urine.
The mean mass balance of radioactivity at 72 h post-dose was 115% (ranging from 112% to 118%) with approximately 6.7% in the remaining carcass. The recovery was considered good.

Toxicokinetic parameters

Toxicokinetic parameters 1

Toxicokinetic parameters:

Cmax: 500 mg/kg bw: 106 µg eq/g (blood); 138 µg eq/g (plasma); 2922 µg eq/g (gastrointestinal tract); 338 µg eq/g (kidneys and adrenals); 332 µg eq/g (liver)

Toxicokinetic parameters 2

Toxicokinetic parameters:

Cmax: 5000 mg/kg bw: 434 µg eq/g (blood); 672 µg eq/g (plasma); 44 050 µg eq/g (gastrointestinal tract); 1533 µg eq/g (kidneys and adrenals); 1691 µg eq/g (liver)

Toxicokinetic parameters 3

Toxicokinetic parameters:

other: 500 mg/kg bw: tmax (blood and plasma): 1 h post administration; tmax (gastrointestinal tract): 1 h, tmax (tissue): 3 h; tmax (adipose tissue): 12 h

Toxicokinetic parameters 4

Toxicokinetic parameters:

other: 5000 mg/kg bw: tmax (blood and plasma): 6 h post administration; tmax (gastrointestinal tract): 1 h; tmax (adipose tissue): 72 h

Toxicokinetic parameters 5

Toxicokinetic parameters:

other: AUC0-tlast: 500 mg/kg bw: 4506 µg eq.h/g (blood value); 4384 µg eq.h/g (plasma value); 15 594 µg eq.h/g (gastrointestinal tract); 13 449 µg eq.h/g (kidneys and adrenals); 13 234 µg eq.h/g (liver)

Toxicokinetic parameters 6

Toxicokinetic parameters:

other: AUC0-tlast: 5000 mg/kg bw: 34 392 µg eq.h/g (blood value); 33 799 µg eq.h/g (plasma value); 515 329 µg eq.h/g (gastrointestinal tract); 116 002 µg eq.h/g (kidneys and adrenals); 129 372 µg eq.h/g (liver)

Toxicokinetic parameters 7

Toxicokinetic parameters:

other: elimination rate constant: 500 mg/kg bw: 0.0125/h (plasma); 0.00928 - 0.0162/h (tissues)

Toxicokinetic parameters 8

Toxicokinetic parameters:

other: elimination rate constant: 5000 mg/kg bw: 0.0134/h (plasma); 0.0112/h (gastrointestinal tract)

Toxicokinetic parameters 9

Toxicokinetic parameters:

half-life 1st: 500 mg/kg bw: 55.6 h (plasma); 43 - 75 h (tissues)

Toxicokinetic parameters 10

Toxicokinetic parameters:

half-life 1st: 5000 mg/kg bw: 51.9 h (plasma); 61.6 - 70.4 (tissues)

Toxicokinetic parameters 11

Toxicokinetic parameters:

other: AUC0-inf: 500 mg/kg bw: 4812 µg eq.h/g

Toxicokinetic parameters 12

Toxicokinetic parameters:

other: AUC0-inf: 5000 mg/kg bw: 36 833 µg eq.h/g (blood/plasma); 526 183 µg eq.h/g (gastrointestinal tract)

Metabolite characterisation studies

Metabolites identified:

not measured

Any other information on results incl. tables

ACTUAL DOSE RECEIVED

test group 2: 516 mg/kg bw

test group 3: 5015 mg/kg bw

test group 4: 5063 mg/kg bw

The mean 14C-radioactivity administered was:

test group 2: 8.45 µCi/animal

test group 3: 6.52 µCi/animal

test group 4: 5.93 µCi/animal

The slightly lower than targeted levels (10 µCi/animal) administered to animals was considered not to impact the outcome of the study since rats were dosed similar amounts of labelled and unlabelled test articles per kg of body weight.

CLINICAL OBSERVATIONS

No treatment related clinical signs were observed in animals prior to or subsequent to treatment with the test item.

LIPID ANALYSES

The recovery from the extraction of the gastrointestinal tract and contents, the liver and the blood was less than 50%. Thus, the radioactivity was associated mainly with water-soluble material. Additionally, the recovery in the blood was lower than 10%. One animal in group 3 showed a recovery of 60.7% in the gastrointestinal tract and contents at 1 hour post-dose. For the perirenal fat, the radioactivity was associated mainly with fat-soluble material.

Thin layer chromatography of organic extracts 1 hour after dosing demonstrated an association of the radioactivity in the gastrointestinal tract and contents with free fatty acids for the low and high-dose group. Further, 12 and 24 hours post-dosing, the radioactivity in the gastrointestinal tract and contents for the high-dose group was mostly associated with diacylglycerides.

Liver extracts revealed an association of the radioactivity with cholesterol for group 3 animals in samples isolated 6 h after administration. However, the exact nature of the main component retained on the origin could not be determined although it was determined for the standards that phospholipids also had an Rf value of 0. In one animal of the low dose group, more than 70% of the radioactivity in the blood extract was cholesterol whereas another animal of the same dose group showed background levels of the radioactivity in the blood extracts. For perirenal fat, the radioactivity in the extracts was also at background level.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): no bioaccumulation potential based on study results