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Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
2011
Reference Type:
study report
Title:
Unnamed
Year:
2011
Report date:
2011

Materials and methods

Objective of study:
toxicokinetics
Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 417 (Toxicokinetics)
Version / remarks:
(1984)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.7485 (Metabolism and Pharmacokinetics)
Version / remarks:
(1998)
Qualifier:
according to guideline
Guideline:
other: Japan/MAFF Guidelines on the Compiling of Test Results on Toxicity; Tests on In Vivo Fate In Animals (2001)
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
Glyoxal
EC Number:
203-474-9
EC Name:
Glyoxal
Cas Number:
107-22-2
Molecular formula:
C2H2O2
IUPAC Name:
oxalaldehyde
Test material form:
liquid
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 954-1012

RADIOLABELLING INFORMATION (if applicable)
- Radiochemical purity: 96.1%
- Specific activity: 69.2 MBq/mg
- Locations of the label: 1,2-C14

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: at low temperatures and in the dark
- Solubility and stability of the test substance in the solvent/vehicle:The analytical investigations performed in the context of this study demonstrated the stability, homogeneity and correctness of the concentrations for the period of the test substance administration of 14C-Glyoxal in the vehicle for all performed experiments.

Radiolabelling:
yes

Test animals

Species:
rat
Strain:
Wistar
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Strain as described in the report: Crl:WI(Han)
- Source: Charles River Laboratories, Research Models and Services, Germany GmbH, Sandhofer Weg 7, 97633 Sulzfeld
- Age at start of acclimatization: 6 to 12 weeks
- Weight at study initiation: 250 - 350 g
- Housing: prior test initiation, in groups in Macrolon cages; during experiment, individually in all-glass metabolism cages type Metabowl (Jencons Leighton Buzzard, U.K.) labeled with the project number, animal number, dose and time of first application
- Diet (e.g. ad libitum): Kliba mouse/rat maintenance diet “GLP” (Provimi Kliba SA, Kaiseraugst, Switzerland), ad libitum
- Water (e.g. ad libitum): Tap water, ad libitum
- Acclimation period: planned, duration not specified

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 30-70
- Air changes (per hr): air-conditioned room
- Photoperiod (hrs dark / hrs light): 12 h/ 12 h
- Any deviations will be documented

ANALYSIS OF FOOD, WATER, BEDDING
- The food used in the study will be assayed for chemical and microbial contaminants according to the Fed. Reg. Vol. 44, No. 91 of May. 09, 1979, p 27354 (EPA);
- The drinking water is regularly assayed for chemical contaminants both by the municipal authorities of Frankenthal and by the Environmental Analytics Water/Steam Monitoring of BASF SE as well as for bacteria by a contract laboratory. The Drinking Water Regulation will serve as the guideline for maximum tolerable contaminants;
- The bedding (Type Lingocel FS 14 fibres, dustfree bedding, supplied by SSNIFF, Soest, Germany) is regularly assayed for contaminants (chlorinated hydrocarbons and heavy metals). The values given in Lab Animal, Nov.–Dec. 1979, pp 24–33, will serve as the guideline for maximum tolerable contaminants.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
CMC (carboxymethyl cellulose)
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
- Radiolabelled and the non-radiolabelled test substance will be prepared in 0.5 % carboxymethylcellulose in tap water.
- For the balance experiments (experiments 4 and 5) and the bile excretion experiments (experiment 8 and 9), the non-radiolabelled test substance will be mixed with the 13C-labelled test substance in a ratio of 1:1 (w:w). In order to achieve the required specific activity, respective amounts of 14C-labelled compound will be added and the mixture will be filled up with 0.5 % carboxymethylcellulose in tap water.

HOMOGENEITY AND STABILITY OF TEST MATERIAL:
The stability, homogeneity and correctness of the concentrations of the test item in the aqueous vehicle will be verified in all experiments by HPLC.
Doses / concentrationsopen allclose all
Dose / conc.:
25 mg/kg bw (total dose)
Remarks:
The required quantity of radioactivity per animal was about 0.2-2 MBq. About 10 mL/kg body weight of a preparation will be administered to rats by gavage. Doses were set to 25 and 250 mg/kg bw.
Dose / conc.:
250 mg/kg bw (total dose)
Remarks:
The required quantity of radioactivity per animal was about 0.2-2 MBq. About 10 mL/kg body weight of a preparation will be administered to rats by gavage. Doses were set to 25 and 250 mg/kg bw.
No. of animals per sex per dose / concentration:
Four males/group
Control animals:
no
Details on study design:
Following series of nine experiments was conducted with a total of 52 animals.

BLOOD AND PLASMA
Test #1: 4 animals dosed with 250 mg/kg bw, total radioactivity was measured in blood and plasma at different time points;
Test #2: 4 animals dosed with 25 mg/kg bw, total radioactivity was measured in blood and plasma at different time points;

BALANCE AND EXCRETION
Test #3: 4 animals dosed with 250 mg/kg bw, total radioactivity was measured in urine, feces, exhaled air (2 animals), and tissue distribution;
Test # 4: 4 animals dosed with 25 mg/kg bw, total radioactivity was measured in urine, feces, exhaled air (2 animals), and tissue distribution;
Test #5: 4 animals dosed with 250 mg/kg bw of non-labelled test material daily during 14 days, and with 250 mg/kg bw of labelled test material on day 15, total radioactivity was measured in urine, feces, exhaled air (2 animals), and tissue distribution;

TISSUE DISTRIBUTION
Test #6: 12 animals dosed with 250 mg/kg bw, sacrifice of 3 animals/time point at 4 different time points, total radioactivity was measured in different tissues;
Test #7: 12 animals dosed with 25 mg/kg bw, sacrifice of 3 animals/time point at 4 different time points, total radioactivity was measured in different tissues;

EXCRETION VIA BILE
Test #8: 4 animals dosed with 250 mg/kg bw, total radioactivity was measured in excreta and tissue;
Test #9: 4 animals dosed with 25 mg/kg bw, total radioactivity was measured in excreta and tissue.
Details on dosing and sampling:
COLLECTION OF SAMPLES
Sampling of blood and plasma:
Blood samples (100 – 200 μL) will be taken from the retroorbital sinus under isoflurane anaesthesia at the following time points or by exsanguination (under isoflurane anaesthesia) at the last time point: 1; 2; 4; 8; 24; 48; 72; 96; 120; 144; 168 hours

Sampling of urine, feces and exhaled air:
The dosed animals will be placed in metabolism cages in order to collect urine after 6, 12 and 24 hours and subsequently in time intervals of 24 hours up to 168 hours and feces in intervals of 24 hours up to 168 hours or until 90 % of the applied radioactivity is excreted, whatever occurs first. In the balance experiments 3 and 4, the first two male animals will be placed in closed metabolism cages in order to additionally collect exhaled air for 48 h. If more than 2 % of the total radioactive dose is detected in exhaled air, all experiments will be carried out in closed systems.After 168 hours, animals will be sacrificed and the following tissues will be checked for remaining radioactivity.

Sampling of organs and tissues:
After sacrifice following tissues will be checked for remaining radioactivity: heart, bone, blood cells and plasma, liver, muscle, pancreas, spleen, kidney, thyroid gland, brain, carcass, adrenal glands, skin, adipose tissue, gut and gut contents, lung, testes, stomach and stomach contents, uterus, ovaries, and bone marrow.

Sampling of bile:
Within experiment 8 and 9, the bile duct cannulated and dosed animals will be placed in metabolism cages in order to collect bile in three-hour time intervals.

Cage wash:
For balance estimates the cage wash will also be checked for radioactivity.

RADIOACTIVITY MEASUREMENT
Radioactivity in all samples of biological material will be counted in a liquid scintillation counter. The samples will be prepared for analysis using conventional methods described in standard operating procedures, any additional measures/deviations from standard practice will be detailed in the raw data and the study report. Unless stated otherwise in this protocol or in the study raw data, total radioactivity is measured.

Results and discussion

Main ADME resultsopen allclose all
Type:
distribution
Results:
highest tissue concentrations were found in the GI tract/GI-tract contents (25 and 250 mg/kg bw)
Type:
excretion
Results:
25 mg/kg bw: urine 13.2%, feces 24.3%, and CO2 about 32%
Type:
excretion
Results:
250 mg/kg bw: urine 12.2%, feces 27.3%, and CO2 about 30%
Type:
other: total recovery of radioactivity
Results:
about 110 and 92% of administered doses (25 and 250 mg/kg bw) were recovered

Toxicokinetic / pharmacokinetic studies

Details on distribution in tissues:
Following a single oral dose of [14C]-Glyoxal at a dose level of 250 mg/kg bw, tissue distribution was measured 24, 72, 120 and 168 hours post-dosing. At the low dose level of 25 mg/kg bw, the corresponding radioactivity measurements were performed 8, 36, 72 and 144 hours after administration. 24 hours after administration of 250 mg/kg bw [14C]-Glyoxal to male rats highest tissue concentrations (means) were found in the GI tractlGi-tract contents. With the exception of the GI-tract (including its content), highest residues (means) in male rats were found in thyroid, bonemarrow, kidney, liver and adrenal glands and lowest mean radioactive residues at this time point were measured in brain and adipose tissue. In male animals, radioactive residue concentrations generally declined in organs and tissues from the 24 h time point on. The residues in organs and tissues declined slower than the plasma concentration. Nearly no clearance could be observed for skin. Lower clearance than in plasma could be observed e.g. for thyroid and carcass. For other organs and tissues the clearance is observed to be about 50 to 75 % within the observation period. 8 hours after administration of 25 mg/kg bw [14C]-Glyoxal to male rats highest tissue concentrations (means) were found in the GI tract/GI-tract contents. With the exception of the GI-tract (including its content), highest residues (means) in male rats of this dose group were found in thyroid, liver, bonemarrow, pancreas and plasma. Lowest mean radioactive residues at this time point were measured in brain and adipose tissue. In male animals, radioactive residue concentrations declined generally in organs and tissues from the 8 h time point on. The residues in organs and tissues declined slower than the plasma concentration. Nearly no clearance could be observed for skin. For other organs and tissues the decrease in residue levels within the observation period was slower than for plama. Lower clearance than in plasma could be observed e.g. for adipose tissue and carcass.
The tissue distribution experiments showed a correlation between the radioactive residues in organs and tissues and the external dose more or less compareable to the Cmax values of plasma. However, the data indicate a slow partition of the radioactive residues between the compartments of the organism. This may be eventually due to the formation of bound residues in the respective matrices.
Details on excretion:
After a single oral administration of 250 mg/kg bw of [14C]-Glyoxal, total recoveries of radioactivity in the balance experiments were > 92 %. In exhaled air, about 30% of the administered radioactivity was excreted as CO2. After 168 hours the total amount of radioactivity excreted in urine was found to be 12.22%. Within 168 hours after single oral administration of 250 mg/kg bw to male rats, 27.30 % of the administered radioactivity were excreted via feces. The time course of the amount of radioactivity found in urine and feces indicates a slow excretion correlating to a residue in carcass after the observation period of one week of up to 30% of the dosed radioactivity. The pattern of excretion after repeated oral administration (14 oral applications with unlabeled Glyoxal at 250 mg/kg bw and one oral application with labeled [14C]-Glyoxal at 250 mg/kg bw) showed higher amounts of radioactivity excreted in urine than in the single dose experiment (21.36 versus 12.22% of dose), lower amounts of excreted radioactivity in feces and higher amounts of exhaled activity but comparable residues in carcass, giving an indication that changes in kinetics 1metabolism occur after multiple dosing of Glyoxal at a dose level of 250 mg/kg. After single oral administration of 25 mg/kg bw the mean total recovery of radioactivity was 109.79% of the administered dose. In exhaled air, about 32% ofthe administered radioactivity was excreted as C02. Within 168 hours after single oral administration of 25 mg/kg bw to male rats, 13.23% of the administered radioactivity were excreted in urine. After 168 hours the total amount of radioactivity excreted via feces was found to be 24.31%. The time course of the amount of radioactivity found in urine and feces indicates a slow excretion correlating to a residue in carcass after the observation period of one week of up to 30% of the dosed radioactivity.
Toxicokinetic parametersopen allclose all
Test no.:
#1
Toxicokinetic parameters:
half-life 1st: 63.5 h
Test no.:
#1
Toxicokinetic parameters:
Tmax: 24 h
Test no.:
#2
Toxicokinetic parameters:
half-life 1st: 65.5 h
Test no.:
#2
Toxicokinetic parameters:
Tmax: 8 h

Metabolite characterisation studies

Metabolites identified:
not measured

Applicant's summary and conclusion