o-toluidine

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication which meets basic scientific principles

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Hepatic macromolecular binding and tissue distribution of ortho- and para-toluidine in rats

Author:

Brock WJ, Hundley SG, Lieder PH

Year:

1990

Bibliographic source:

Toxicol Lett 54: 317-325

Reference 2

Reference Type:

publication

Title:

o-TOLUIDINE CAS No: 95-53-4 SIDS Initial Assessment Report.

Author:

OECD

Year:

2006

Bibliographic source:

UNEP Publications

Materials and methods

Objective of study:

distribution

Principles of method if other than guideline:

The tissue distribution of o-toluidine was investigated

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

o-toluidine

EC Number:

202-429-0

EC Name:

o-toluidine

Cas Number:

95-53-4

Molecular formula:

C7H9N

IUPAC Name:

2-methylaniline

Details on test material:

Name: o-[ring-U-14C]-toluidine
Activity: 18.5 mCi/mmol)
Source: Amersham (Arlington Heights)
Radiochemical purity (if radiolabelling): 99%

Name: o-Toluidine (unlabeled)
Source: Aldrich Chemicals Co (Milwaukee, WI, USA)

Radiolabelling:

yes

Remarks:

14-C

Test animals

Species:

rat

Strain:

other: Crl:CD®BR

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, NY)
- Individual metabolism cages: individually in suspended, stainless-steel, wire-mesh cages
- Diet (e.g. ad libitum): ad libitum, ad libitum, provided by Purina Certified Rodent Chow #5002
- Water (e.g. ad libitum): ad libitum

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: Corn oil/methanol (8:2, v/v)

Details on exposure:

VEHICLE
- Concentration in vehicle: no data
- Purity: no data

Duration and frequency of treatment / exposure:

After a single oral application of the test substance, blood was drawn via a previously inserted jugular-vein cannula at 0.5, 2, 6, 12, 24, 48 and 72h

Doses / concentrations

Remarks:

Doses / Concentrations:
In a 2mL dosing volume, a concentration of 500 mg/kg bw in corn oil/methanol (1mCi, 0.095µCi/mg) was administered

No. of animals per sex per dose / concentration:

4 animals per time point

Control animals:

no

Details on study design:

- The dosage of 500 mg/kg bw was chosen because it represented an approximate equivalent (in mg/kg bw) of the dietary level fed to rats and mice that produced tumors in the longterm carcinogenicity studies.

National Cancer Institute (1979) Bioassay of o-toluidine hydrochloride for carcinogenicity. NCICGTR153,
Weisburger et al. (1978). Environ. Pathol. Toxicol. 2,325-356.1,2].

- Lower dosage levels were not considered because of the sensitivity of the RNA and DNA assays which were also co-employed in the study

Details on dosing and sampling:

- Blood was drawn at time points 0.5h, 2h, 6h, 12h, 24h, 48h and 72h and centrifuged (plasma and whole fractions). The plasma fractions were assayed directly by liquid scintillation counting. Areas under the plasma concentration-time curves (AUC) were determined by the trapezoidal method after using the plasma half-life to extrapolate to a plasma concentration of zero.

Gibaldi, M. and Perrier, D. (1975) Phamacokinetics. Marcel Dekker, Inc., New York.

- After 72 h, the rats were sacrificed after dosing by chloroform anesthesia. Selected organ and tissue samples (not exceeding 0.50 g) were subsequently assayed for radioactivity by tissue combustion (Packard Model 306 Tissue Oxidizer) and scintillation counting.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

Peak blood levels were observed for the o-toluidine after 24h.

Details on distribution in tissues:

Tissue distribution of o-toluidine after 72h: Whole blood > Spleen > kidneys > Liver > Subcutaneous abdominal fat ~ Lungs > Heart ~ Abdominal skin > Bladder > GI Tract ~ Bone marrow > Brain ~ muscle (thigh) > Testes

Details on excretion:

Elimination of radioactivity primarily via urine (the publication cited a private communication with Hundley S.G)

Toxicokinetic parameters

Toxicokinetic parameters 1

Test no.:

#1

Toxicokinetic parameters:

AUC: - 2.9 mg hr/ml (Area under curve)

Toxicokinetic parameters 2

Test no.:

#2

Toxicokinetic parameters:

half-life 1st: 12-15 h (Area under curve)

Metabolite characterisation studies

Metabolites identified:

not measured

Any other information on results incl. tables

Table 1: Tissue and organ concentration following single oral dose of o-toluidine.

Organ or tissues	Concentration (µg Eq./g tissue)
Whole blood	22.6 ± 6.8
Spleen	19.2 ± 10.8
Kidneys	17.2 ± 2.5
Liver	16.3 ± 3.2
Subcutaneous abdominal fat	6.9 ± 5.4
Lungs	6.8 ± 2.1
Heart	4.8 ± 1.4
Abdominal skin	4.4 ± 0.7
Bladder	3.7 ± 1
GI tract	2.7 ± 0.8
Bone marrow	2.2 ± 1.1
Brain	1.6 ± 0.6
Muscle (thigh)	1.5 ± 0.3
Testes	1.0 ± 0.3

All the values are the mean (± SD). GI contents were removed before the tissue was assayed for radioactivity.

Applicant's summary and conclusion

Executive summary:

Brock (1990)

The tissue distribution of o-toluidine was measured. 72 hours following oral application to rats, radioactivity was detected in decreasing range: whole blood > spleen > kidney > liver > subcutaneous abdominal fat > lung > heart > abdominal skin> bladder >gastrointestinal tract > bone marrow > brain > muscle > testes. Following oral application of 500 mg toluidine/kg bw to rats a half-life time of plasma elimination of 12 to 15 hours was also derived.