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Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: K2 since being used for read-across.
Cross-reference
Reason / purpose:
read-across: supporting information
Reference
Endpoint:
basic toxicokinetics in vivo
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reason / purpose:
read-across source
Details on absorption:
No deaths occurred during the study. No compound-related clinical signs of toxicity were observed in the rats dosed with the test substance. Rats dosed with a positive control material, potassium perfluoroalkyl sulfonate, exhibited diarrhea, salivation, alopecia, black ocular discharge, and staining of various parts of the body during the dosing period. Rats dosed with ammonium perfluorooctanoate, the other positive control substance, exhibited wet perineum and diarrhea during the dosing period. Alopecia was observed during the recovery period for rats dosed with the test substance and both positive control substances. The negative control rats exhibited no clinical signs during the study. Accounting for the age difference at study start and the expected rate of body weight gain, the mean body weights and mean body weight gains of the rats dosed with the test substance were comparable to the negative controls and equal to or greater than the positive controls.
Blood fluorine levels: A steady-state for fluorine levels in whole blood was not achieved during 10 consecutive days of dosing with 1000 mg/kg test substance. An area under the curve (estimated to infinity) was calculated and normalized for fluorine content for the test substance and each positive control. The AUCINF/D for the fluorine component of the test substance was 1750, compared to AUCINF/D values of 566,479.1 and 70,789.6 for potassium perfluoroalkyl sulfonate and ammonium perfluorooctanoate, respectively.
Liver weights: The mean relative liver weight (liver/body weight) of rats dosed with the test substance was up to 25% higher than the negative controls on day 10. By day 94, the weights were similar. On day 10, the mean relative liver weight of rats dosed with the positive control potassium perfluoroalkyl sulfonate was up to 27% higher than the negative controls. By day 94, the mean relative liver weight was up to 28% higher than the negative controls. In rats given ammonium perfluorooctanoate, the mean relative liver weight was up to 75% higher at day 10 than the negative controls. By day 94, the weights were similar.
Liver fluorine levels: Levels of total fluorine in livers from rats dosed with the test substance were lower than the levels in livers from rats dosed with the positive control materials potassium perfluoroalkyl sulfonate and ammonium perfluorooctanoate. The total fluorine concentration in the liver from rats dosed with the test substance was 101.28 μM equivalents at day 10 and 5.14 μM equivalents at day 94. For the positive control potassium perfluoroalkyl sulfonate, the liver concentrations were approximate ly 50x higher (day 10) and approximately 230x higher (end of study) than the test substance. For ammonium perfluorooctanoate, the liver concentrations were approximately 11x higher (end of dosing) and approximately 2x higher (end of study) than the test substance. The μM equivalents of fluorine in the livers from rats dosed with the test substance were higher than levels in the blood.

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
2000
Report Date:
2000
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report Date:
2001

Materials and methods

Objective of study:
absorption
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The objective of this study was to define the potential of the test substance when administered by gavage, to be absorbed and to accumulate in a mammalian system, as indicated by analytical determination of total fluorine in blood and liver. The test substance was compared to 2 positive controls that were materials previously shown to bioaccumulate in mammals. All blood samples and selected liver samples were analyzed for total fluorine content.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Purity: not reported as such
Radiolabelling:
no

Test animals

Species:
rat
Strain:
other: Crl:CD®(SD)IGS BR
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: between 7 and 9 weeks of age at the time of dosing
- Weight at study initiation: 245.3 g (mean body weight)
- Fasting period before study: Not reported
- Housing: Singly in stainless steel, wire-mesh cages suspended above cage boards.
- Individual metabolism cages: No
- Diet (e.g. ad libitum): Certified rodent chow ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 ± 1°C
- Humidity (%): 50 ± 10%
- Air changes (per hr): Not reported
- Photoperiod (hrs dark / hrs light): Approximate 12-hour light/dark cycle (fluorescent light)

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
unchanged (no vehicle)
Details on exposure:
PREPARATION OF TEST SUBSTANCE FORMULATION: The test substance was dosed as received. The amount of test substance each rat received was based on the body weight collected on each day of dosing and the test substance density of 1150 mg/mL. The test substance was stirred on a magnetic stir plate throughout the dosing procedure.
Duration and frequency of treatment / exposure:
The test substance, the two negative controls, and the two positive controls were each administered to one group of 5 rats for 5 consecutive days and to 5 groups for 10 days.
Doses / concentrations
Remarks:
Doses / Concentrations:
1000 mg/kg/day (test substance); 10 mg/kg/day (positive control, potassium perfluoroalkyl sulfonate); 20 mg/kg/day (positive control, ammonium perfluorooctanoate)
No. of animals per sex per dose:
5 males for 5 day exposure, 25 males for 10 day exposure
Control animals:
other: Corn oil and corn oil:acetone (80:20) were chosen as the negative controls because they were the vehicles for the positive controls. Each negative control rat received 1 mL of corn oil or corn oil:acetone.
Positive control:
The solid positive control compounds were suspended as emulsions in their respective vehicles. Corn oil was used as the vehicle for ammonium perfluorooctanoate. It was necessary to dissolve potassium perfluoroalkyl sulfonate in acetone before suspending it in corn oil. The ratio of acetone to corn oil was 20:80. The amount each rat received was based on the body weight collected on each day of dosing and the suspension concentration. The dose volumes did not exceed 1 mL/100 g of body weight. The dosing suspensions were stirred on a magnetic stir plate throughout the dosing procedure to maintain homogeneity.
Details on study design:
- Dose selection rationale: The dosage of 1000 mg/kg/day was chosen based on available toxicity data and the results of a rangefinding study. In the rangefinding study, a group of 5 male rats was dosed by oral gavage with the test substance at a dosage of 2000 mg/kg for 5 consecutive days. A group of 5 male rats was dosed with deionized water for 5 consecutive days and served as controls. The rats dosed with the test substance experienced an overall mean body weight gain of 13 grams. The control group had an overall mean body weight gain of 27 grams. A dosage of 1000 mg/kg was selected for the limit dosage for this project. The limit dosage of 1000 mg/kg was chosen for the main study and was expected to produce less than a 10% difference in mean body weight over 10 days when compared to controls.
- Rationale for animal assignment (if not random): After the quarantine period, the rats were selected on the bases of adequate body weight gain, freedom from any clinical signs of disease or injury, and a body weight within ± 20% of the mean. The selected rats were divided by computerized, stratified randomization into 6 groups of 5 rats, so that there were no statistically significant differences among group body weight means.
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Blood and liver.
- Time and frequency of sampling: Approximately 2 hours after the first dose, blood was collected from the orbital sinus of each rat from the 5-dose group. On selected days (5, 10, 13, 24, 52, 94) 5 rats per group were euthanized and the blood and livers were collected. Livers were weighed and those collected on study days 10 and 94 were analyzed for total fluorine. All blood samples were analyzed for total fluorine content. The negative and positive controls were similarly tested.
Statistics:
Noncompartmental analysis was conducted on blood fluorine data derived from rats dosed with with the test substance by using WinNonlin Version 3.0 software (Pharsight Corp, Mountain View, CA). WinNonlin software provided a means of computing derived pharmacokinetic parameters from data files including area under the curve (AUCINF), Cmax and terminal half-life (T1/2). The AUCINF (concentration x time) represents the area under the blood concentration curve from the time of dosing extrapolated to infinity. The maximum observed concentration was Cmax (concentration). The points included in determination of the terminal half-life were selected manually and given in units of time. Since the dosages and fluorine content for each positive control and the test material varied, all doses were normalized to 0.1 mmole/kg for comparative purposes. The accumulation index (AI, 1/(1-e-kt)) and bioaccumulation index (BI, Cmax x AI) were calculated and reported but not further use.
Dosing diluents were used as negative controls, but because of variability and limited sensitivity of the analytical method, the background was set at 0.2 ppm fluorine. Since 0.2 ppm was the fluoride concentration limit of detection, any values listed as <0.2 ppm were excluded from further treatment.
The percent of fluorine and molecular weight of the test substance and positive controls were used as provided by the sponsor. The measurements resulting from analysis of total blood fluorine were used as received (ppm F). Fluoride ion was converted to micromolar (μM) equivalents of active component for further comparisons.

Results and discussion

Preliminary studies:
See Details on study design

Toxicokinetic / pharmacokinetic studies

Details on absorption:
No deaths occurred during the study. No compound-related clinical signs of toxicity were observed in the rats dosed with the test substance. Rats dosed with a positive control material, potassium perfluoroalkyl sulfonate, exhibited diarrhea, salivation, alopecia, black ocular discharge, and staining of various parts of the body during the dosing period. Rats dosed with ammonium perfluorooctanoate, the other positive control substance, exhibited wet perineum and diarrhea during the dosing period. Alopecia was observed during the recovery period for rats dosed with the test substance and both positive control substances. The negative control rats exhibited no clinical signs during the study. Accounting for the age difference at study start and the expected rate of body weight gain, the mean body weights and mean body weight gains of the rats dosed with the test substance were comparable to the negative controls and equal to or greater than the positive controls.
Blood fluorine levels: A steady-state for fluorine levels in whole blood was not achieved during 10 consecutive days of dosing with 1000 mg/kg test substance. An area under the curve (estimated to infinity) was calculated and normalized for fluorine content for the test substance and each positive control. The AUCINF/D for the fluorine component of the test substance was 1750, compared to AUCINF/D values of 566,479.1 and 70,789.6 for potassium perfluoroalkyl sulfonate and ammonium perfluorooctanoate, respectively.
Liver weights: The mean relative liver weight (liver/body weight) of rats dosed with the test substance was up to 25% higher than the negative controls on day 10. By day 94, the weights were similar. On day 10, the mean relative liver weight of rats dosed with the positive control potassium perfluoroalkyl sulfonate was up to 27% higher than the negative controls. By day 94, the mean relative liver weight was up to 28% higher than the negative controls. In rats given ammonium perfluorooctanoate, the mean relative liver weight was up to 75% higher at day 10 than the negative controls. By day 94, the weights were similar.
Liver fluorine levels: Levels of total fluorine in livers from rats dosed with the test substance were lower than the levels in livers from rats dosed with the positive control materials potassium perfluoroalkyl sulfonate and ammonium perfluorooctanoate. The total fluorine concentration in the liver from rats dosed with the test substance was 101.28 μM equivalents at day 10 and 5.14 μM equivalents at day 94. For the positive control potassium perfluoroalkyl sulfonate, the liver concentrations were approximately 50x higher (day 10) and approximately 230x higher (end of study) than the test substance. For ammonium perfluorooctanoate, the liver concentrations were approximately 11x higher (end of dosing) and approximately 2x higher (end of study) than the test substance.
The μM equivalents of fluorine in the livers from rats dosed with the test substance were higher than levels in the blood.

Applicant's summary and conclusion

Conclusions:
Under the conditions of this study, administration of the test substance to male rats for 10 consecutive days resulted in limited absorption and retention of fluorine in the blood and liver. For blood, dose-adjusted areas under the curve (AUCINF/D) for the positive controls were approximately 320x and 40x the AUCINF/D for the fluorine component of the test substance. Liver weights were elevated in rats dosed with the test substance at the end of the dosing period, but not at the end of the recovery period. Fluorine levels in the liver were significantly lower than levels in rats dosed with the positive control materials. The μM equivalents of fluorine in the livers from rats dosed with the test substance were higher than levels in the blood.
Executive summary:

The objective of this study was to evaluate the potential for the test substance, when administered by gavage, to be absorbed and to accumulate in a mammalian system as indicated by analytical determination of total fluorine in blood and liver. The test substance, the two negative controls (corn oil and corn oil:acetone) and the two positive controls (potassium perfluoroalkyl sulfonate and ammonium perfluorooctanoate) were each administered to one group of 5 rats for 5 consecutive days and to 5 groups for 10 days. All rats dosed with the test substance survived and exhibited no compound-related clinical signs of toxicity.

A steady-state for fluorine levels in whole blood was not achieved during 10 consecutive days of dosing with 1000 mg/kg test substance. An area under the curve (estimated to infinity) was calculated and normalized for fluorine content for the test substance and each positive control. The AUCINF/D for the fluorine component of the test substance was 1750, compared to AUCINF/D values of 566,479.1 and 70,789.6 for potassium perfluoroalkyl sulfonate and ammonium perfluorooctanoate, respectively.

The mean relative liver weight (liver/body weight) of rats dosed with the test substance was up to 25% higher than the negative controls on day 10. By day 94, the weights were similar. On day 10, the mean relative liver weight of rats dosed with the positive control potassium perfluoroalkyl sulfonate was up to 27% higher than the negative controls. By day 94, the mean relative liver weight was up to 28% higher than the negative controls. In rats given ammonium perfluorooctanoate, the mean relative liver weight was up to 75% higher at day 10 than the negative controls. By day 94, the weights were similar.

Levels of total fluorine in livers from rats dosed with the test substance were lower than the levels in livers from rats dosed with the positive control materials potassium perfluoroalkyl sulfonate and ammonium perfluorooctanoate. The total fluorine concentration in the liver from rats dosed with the test substance was 101.28 μM equivalents at day 10 and 5.14 μM equivalents at day 94. For the positive control potassium perfluoroalkyl sulfonate, the liver concentrations were approximately 50x higher (day 10) and approximately 230x higher (end of study) than the test substance. For ammonium perfluorooctanoate, the liver concentrations were approximately 11x higher (end of dosing) and approximately 2x higher (end of study) than ammonium perfluorooctanoate.

The μM equivalents of fluorine in the livers from rats dosed with the test substance were higher than levels in the blood.