Tungsten trioxide

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-01-28 To: 2009-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2009

Materials and methods

Objective of study:

absorption

Test guideline

Qualifier:

according to guideline

Guideline:

other: Draft Guidance for RIP 3.6: Bioavailability and Read-Across for Metals and Minerals

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Tungsten trioxide

EC Number:

215-231-4

EC Name:

Tungsten trioxide

Cas Number:

1314-35-8

Molecular formula:

O3W

IUPAC Name:

trioxotungsten

Details on test material:

- Name of test material (as cited in study report): Tungsten Trioxide
- Substance type: Pure active substance
- Physical state: Solid

Radiolabelling:

no

Test animals

Species:

other: Human simulated fluids

Strain:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

no data

Administration / exposure

Route of administration:

other: In vitro study

Details on exposure:

Preparation of Testing Fluids: The simulated fluids used in this study were gastric, lung alveolar, lung interstitial, lysosomal and artificial sweat. All salts and reagents used for the simulated fluid preparation were obtained from Sigma-Aldrich (St. Louis, MO).

Extraction Experiments: Extractions of the test substances in the simulated fluids were performed at pre-set time periods (up to 72 hours) while protected from light, using 0.1 g of sample in 50 ml of simulated fluid, at 37 C and with continuous shaking (for all fluids except sweat, for which only initial shaking was performed). The experiments were carried out as follows:
- Simulated Gastric Fluid: The reactions were sampled for the determination of tungsten at 5 hours.
- Simulated Interstitial, Alveolar and Lysosomal Fluids: 5% CO2 in nitrogen was bubbled into solution at a rate of 50 ml/min. The reactions were sampled for the determination of tungsten at 2, 5, 24, and 72 hours.
- Simulated Sweat: The reactions were sampled for the determination of tungsten after 12 hours. No shaking was performed after the initial set up.

Sample Preparation: The simulated fluid extract samples were filtered immediately after sampling using 50 ml centrifuge tubes equipped with 0.45 microns PVDF filters (Grace Alltech, Deerfield, IL). The filtrates were stored in plastic bottles at 35 C until analysis.

The extracts were then analyzed for tungsten by inductively coupled plasma-mass spectrometry (ICP-MS).

Duration and frequency of treatment / exposure:

Single application of tungsten with fluids. Simulated Gastric Fluid was sampled for the determination of tungsten at 5 hours. Simulated Interstitial, Alveolar and Lysosomal Fluids were sampled for the determination of tungsten at 2, 5, 24, and 72 hours. Simulated Sweat was sampled for the determination of tungsten after 12 hours.

Doses / concentrations

Remarks:

Doses / Concentrations:
0.1 g of test substance in 50 mL of simulated fluid

Control animals:

no

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Simulated gastric fluid, Simulated interstitial fluid, Simulated alveolar fluid, Simulated lysosomal fluid and Simulated sweat
- Time and frequency of sampling: Simulated gastric fluid sampled at 5 hours, Simulated interstitial fluid sampled at 2, 5, 24, and 72 hours, Simulated alveolar fluid sampled at 2, 5, 24, and 72 hours, Simulated lysosomal fluid sampled at 2, 5, 24, and 72 hours and Simulated sweat sampled after 12 hours.

Sample analysis: Samples were diluted (if necessary), spiked with an internal standard [bismuth (Bi) at 1,000 pg/mL, prepared from dilution of a 1,000 ug/mL Certified Standard; Ultra Scientific, North Kingston, RI and analyzed directly on a Perkin Elmer Elan DRC II ICP-MS equipped with a dynamic reaction cell (DRC) and PerkinElmer AS-93 Plus autosampler instrument, according to methods established at IITRI for this study. A standard curve (prepared from dilutions of a 10,000 5%HNO3/6% HF; inorganic Ventures, Lakewood, NJ] was analyzed along with samples on each day of analysis. Instruments calibrators were prepared by diluting Certified Standard with 0.5% nitric acid to concentrations of approximately 200; 400; 800; 1,600; 3,200; 6,400; 13,000; and 25,000 pg/mL.

Statistics:

Calibration curves, regression coefficients and r-squared values were calculated using PerkinElmer ICP-MS software and Microsoft Excel software. Concentration values of tungsten in the study samples were calculated from linear regression coefficients derived from calibration standards that bracketed the expected concentration levels of tungsten in the study samples.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

The fluid extracts were diluted 1:50 to 1:125000 for analysis. The average amount of tungsten found in the extracts was in the 0.0055 to 39% range. The maximum solubility was determined at 72 hours for the simulated alveolar, lysosomal and interstitial fluids (34, 38 and 39%, respectively). %RSDs ranged from 2.5 to 37%.

Toxicokinetic parameters

Toxicokinetic parameters:

other: not applicable

Bioaccessibility (or Bioavailability)

Bioaccessibility (or Bioavailability) testing results:

Gastric Fluid: The mean percent of available tungsten in simulated gastric fluid sampled at 5 hours was 0.0055 +/- 0.00026 % (4.7 % relative standard deviation). Sweat Fluid: The mean percent of available tungsten in simulated sweat fluid sampled at 12 hours was 7.9 +/- 1.3 % (17 % relative standard deviation). Alveolar Fluid: The mean percent of available tungsten in simulated alveolar fluid sampled at 2, 5, 24, and 72 hours was 2.4 +/- 0.18, 7.5 +/- 0.51, 18 +/- 2.5, and 34 +/- 6.1 %, respectively; the percent relative standard deviation for the 2, 5, 24, and 72 hours was 7.5, 6.8, 13 and 18 %RSD, respectively. Lysosomal Fluid: The mean percent of available tungsten in simulated lysosomal fluid sampled at 2, 5, 24, and 72 hours was 0.49 +/- 0.014, 1.3 +/- 0.032, 18 +/- 2.6, and 38 +/- 1.3 %, respectively; the percent relative standard deviation for the 2, 5, 24, and 72 hours was 2.8, 2.5, 15, and 3.5 %RSD, respectively. Interstitial Fluid: The mean percent of available tungsten in simulated interstitial fluid sampled at 2, 5, 24, and 72 hours was 2.3 +/- 0.83, 11 +/- 2.8, 23 +/- 4.3, and 39 +/- 1.6 %, respectively; the percent relative standard deviation for the 2, 5, 24, and 72 hours was 37, 25, 19, and 4.1 %RSD, respectively.

Applicant's summary and conclusion

Conclusions:

In a GLP in vitro study conducted according to Draft Guidance for RIP 3.6: Bioavailability and Read-Across for Metals and Minerals, the bioavailability of tungsten trioxide was determine in human gastric, sweat, alveolar, lysosomal, and interstitial fluids. The mean percent of available tungsten in simulated gastric fluid sampled at 5 hours was 0.0055 % (4.7 % relative standard deviation). The mean percent of available tungsten in simulated sweat fluid sampled at 12 hours was 7.9 (17 % relative standard deviation). The mean percent of available tungsten in simulated alveolar fluid sampled at 2, 5, 24, and 72 hours was 2.4, 7.5, 18, and 34, respectively; the percent relative standard deviation for the 2, 5, 24, and 72 hours was 7.5, 6.8, 13 and 18 %RSD, respectively. The mean percent of available tungsten in simulated lysosomal fluid sampled at 2, 5, 24, and 72 hours was 0.49, 1.3, 18, and 38%, respectively; the percent relative standard deviation for the 2, 5, 24, and 72 hours was 2.8, 2.5, 15, and 3.5 %RSD, respectively. The mean percent of available tungsten in simulated interstitial fluid sampled at 2, 5, 24, and 72 hours was 2.3, 11, 23, and 39%, respectively; the percent relative standard deviation for the 2, 5, 24, and 72 hours was 37, 25, 19, and 4.1 %RSD, respectively. The bioavailability in the fluids ranged from 0.0055% (gastric fluid) to 39% (interstitial fluid). The maximum solubility was determined at 72 hours for the simulated alveolar, lysosomal and interstitial fluids (34, 38 and 39%, respectively). Based on the results, the bioavailability of tungsten trioxide would be expected to be low for the oral route of administration, but moderate for inhalation route.