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Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: - scientifically sound study, generally guideline compliant - non-GLP

Data source

Reference
Reference Type:
publication
Title:
Comparative disposition and metabolism of 1,2,3-trichloropropane in rats and mice.
Author:
Mahmood NA, Overstreet D & Burka LT.
Year:
1991
Bibliographic source:
Drug Metab Dispos. 1991 Mar-Apr;19(2):411-8.

Materials and methods

Objective of study:
absorption
distribution
excretion
metabolism
Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Deviations:
yes
Remarks:
: only one dose level used in rats
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 1,2,3-trichloropropane
- Substance type: chlorinated short-chain hydrocarbon
- Physical state: liquid
- Analytical purity: unlabeled substance: 98 %; labeled substance: > 93 %
- Impurities (identity and concentrations): unlabeled: not reported; labeled: major radiochemical impurity (ca. 5%) is thought to be 2-[ 14C]2,3-dichloropropene
- Purity test date: not reported
- Lot/batch No.: not reported
- Provider: unlabeled substance: Fluka Chemical Corp. (Ronkonkoma, NY); labeled substance: DuPont Biomedical Products (Boston, MA).
- Expiration date of the lot/batch: not reported
- Radiochemical purity (if radiolabelling): labeled substance > 93 %
- Specific activity (if radiolabelling): labeled substance 57 mCi/mmol,
- Locations of the label (if radiolabelling): 2-[ 14C]1,2,3-TCP
- Expiration date of radiochemical substance (if radiolabelling): not reported
- Stability under test conditions: not reported, expected to be stable
- Storage condition of test material: not reported
Radiolabelling:
yes

Test animals

Species:
other: rat and mouse
Strain:
other: F344 rats and B6C3F1 mice
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Wilmington, MA).
- Age at study initiation: not reported
- Weight at study initiation: Male rats: 180-250 g, Female rats: 170-180 g, Male mice: 30 g
- Fasting period before study: no
- Housing: individually in the metabolism cages for separate collections of excreta or Metabowl-Mark III glass metabolism cages (Jencons, Hemel Hempstead, Herfordshire, UK) for analysis of exhaled air
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): rat chow, ad libitum
- Water (e.g. ad libitum): water, ad libitum
- Acclimation period: not reported


ENVIRONMENTAL CONDITIONS
- not reported

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:


VEHICLE
- Justification for use and choice of vehicle (if other than water): not reported, but cornoil is a standard vehicle for volatile lipophilic solvents like 1,2,3-trichloropropane
- Concentration in vehicle: rats: 6 mg/mL, mice: 30 or 60 mg/7 mL
- Amount of vehicle (if gavage): rats: 5 mL/Kg bw, mice 7 mL/Kg bw
- Lot/batch no. (if required): not reported
- Purity: not reported


HOMOGENEITY AND STABILITY OF TEST MATERIAL:
as 1,2,3-trichloropropane is a stable lipophilic solvent the homogeneity and stability of the the test material is of no concern
Duration and frequency of treatment / exposure:
single treatment via gavage
Doses / concentrations
Remarks:
Doses / Concentrations:
rats: 30 mg/Kg bw
mice: 30, 60 mg/Kg bw
No. of animals per sex per dose:
- unclear from the report
- 3 animals were analysed per time point
Control animals:
no
Positive control:
no
Details on study design:
- Dose selection rationale:
- Rationale for animal assignment (if not random):
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled (delete / add / specify): urine, faeces, blood, plasma, serum or other tissues, cage washes, bile
- Time and frequency of sampling:
- Other:


METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled (delete / add / specify): urine, faeces, tissues, cage washes, bile
- Time and frequency of sampling:
- From how many animals: (samples pooled or not)
- Method type(s) for identification (e.g. GC-FID, GC-MS, HPLC-DAD, HPLC-MS-MS, HPLC-UV, Liquid scintillation counting, NMR, TLC)
- Limits of detection and quantification:
- Other:


TREATMENT FOR CLEAVAGE OF CONJUGATES (if applicable): not applicable
Statistics:
Statistical analysis was performed using a pairwise comparison of variance (one-sided t test). Values were considered statistically significant at p -.5 0.05.

Results and discussion

Preliminary studies:
no data

Toxicokinetic / pharmacokinetic studies

Details on absorption:
1,2,3-trichloropropane is rapidly absorbed as can be expected for a small lipophilic chlorinated solvent molecule (see table 1 for details).
Details on distribution in tissues:
1,2,3-trichloropropane is easily distributed to all tissues via the blood circulation.
After 6 h post dosing the highest concentrations in male rats are found in fore stomach, glandular stomach, small and large intestine, adipose tissue liver and kidneys (see table 1)
Between 6 and 24 h in male rats the concentration of radioactivity rised markedly in the liver and in the kidneys and in all other tissues, while declining in stomach (drastically), intestine, lung and spleen. No significant difference in any tissue was found at this timepoint between male and female rats.
60 h post dosing the highest concentration of radioactivity was present in the liver, kidneys and fore stomach of rats of both sexes. In females in all three tissues concentrations were higher than in males though statistically significant only for the fore stomach.
Male mice after 60 h showed generally the same distribution pattern of radioactivity as compared to rats but the concentrations of the 30 mg/Kg dose group have generally lower levels than the rats that were dosed also with 30 mg/Kg bw (see table 2). The 60 mg/Kg bw mice on the other hand showed radioactivity levels comparable to the 30 mg/Kg dosed rats.
The relative distribution of the radioactivity did not vary with the different doses in mice. On the contrary the tissues concentrations are roughly proportional to the dose.
50 to 80 % of the radioactivity of the tissues of rats at 24 and 60 h were not extractable indicating that 1,2,3-trichloropropane and/or its metabolites react with cellular constituents.
The different radioactivity levels found in equally dosed rats and mice is in good agreement with the higher tolerance of mice towards 1,2,3-trichloropropane in repeated dose experiments and indicates a faster metabolism in mice compared to rats.
The blood brain barrier is not effective against 1,2,3-trichloropropane as the brain shows generally the same concentration levels as the blood.
Transfer into organs
Test no.:
#1
Transfer type:
blood/brain barrier
Observation:
distinct transfer
Details on excretion:
> 90 % of the 1,2,3-trichloropropane derived radioactivity was excreted within 60 h post dosing in male and female rats and mice (see table 4).
There is no significant difference in the pattern of excretion routes between rats and mice (see table 4).
The major route is via urine (50 - 60 %) while feces and exhalation (mainly as carbon dioxide, only 2 % as unchanged 1,2,3-trichloropropane) account both for approximately 20 % at 60 h.
At 24 h already more than 50 % of the administered radioactivity was excreted in total in rats.
No significant sex differences were found in rats.
Mice exhaled radioactive carbon dioxide significantly faster than rats proposing a faster metabolism in rats.
Kinetics of excretion via the different routes were not significantly different in the two mice dose groups.
Toxicokinetic parameters
Test no.:
#1
Toxicokinetic parameters:
other: 24 h already more than 50 % of the administered radioactivity was excreted in total in rats

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
About 20 % of the administered radioactivity were exhaled as carbon dioxide indicating extensive metabolisation in both species.
In rat urine the major metabolite (40 % of radioactivity) is N-acetyl-S-(3-chloro-2-hydroxypropy1)-L-cysteine (ACPC), a mercapturic acid that might be a product either of cytochrome P450 mediated oxidation at C2 (forming dichloroacetone) followed by reaction with glutathion and finally reduction to the respective alcohol or by direct nucleophilic substitution of two chlorine atoms, forming an intermediate sulfonium ion which is later hydrolized. The intermediate sulfonium ion species as well as the dichloroacetone are reactive molecules that can interact with biologic macromolecules.
ACPC is only a minor metabolite in mice urine while S-(3-chloro-2-hydroxypropy1)-L-cysteine (CPC) is the second most abundant metabolite in mice urine.
The major metabolite in mice urine could not be identified.
The major metabolite of rat bile is 2-(S-glutathionyl)malonic acid (GMA) also a metabolite indicative of a combination of oxidative metabolism plus glutathion scavenging.

Any other information on results incl. tables

- table 1: Concentration (µg eq/g tissue) of radioactivity in tissues of male and female F344 rats following administration of 30 mg/kg of [14C]-1,2,3-trichloropropane vs. time

Tissue

6 hr

24 hr

60 hr

 

Male

Male

Female

Male

Female

Blood

1.6 ± 0.4

3.1 ± 0.4

2.3 ± 0.3

1.5 ± 0.4

3.2 ± 0.9

Liver

12.6 ± 5.2

20.4 ± 5.2

24.1 ± 2.7

8.6 ± 1.4

11.0± 1.5

Kidney

14.3 ± 2.4

16.8 ± 4.3

22.5 ± 1.1

8.0 ± 1.6

13.1 ± 3.2

Skin

1.5 ± 0.4

2.6 ± 0.6

2.8 ± 0.5

1.6 ± 0.2

2.2 ± 0.3

Adipose

26.5 + 6.4

4.3 ± 1.3

1.9 ± 0.8

0.8 ± 0.1

1.7 ± 0.8

Muscle

0.8 ± 0.1

1.3 ± 0.6

1.0 ± 0.3

0.6 ± 0.2

0.7 ± 0.2

Brain

1.8.1. 0.7

33 ± 1.1

3.7 ± 0.2

1.9 ± 0.4

2.4 ± 0.1

Spleen

6.7 ± 5.0

3.7 ± 1.6

5.3 ± 0.6

1.9 ± 0.6

3.3 ± 0.0 a

Lungs

4.9 ± 2.4

3.4 ± 0.8

4.8 ± 0.1

2.0 ± 0.1

3.2 ± 0.6

Heart

2.0 ± 0.7

3.9 ± 1.0

3.7 ± 0.9

2.2 ± 1.1

3.0 ± 0.5

Stomach

 

 

 

 

 

  Fore

21.5.6 ± 18.0

33.7 ± 18.9

25.8 ± 2.6

5.7 ± 0.5

11.6 ± 2.2 a

  Glandular

98.7 ± 3E4

11.6 ± 5.9

7.8 ± 2.7

2.4 ± 0.2

3.3 ± 0.5

Intestine

 

 

 

 

 

  Small

54.0 ± 17.1

9.5 ± 3.9

9.6 ± 4.0

1.9 ± 1.9

3.1 ± 0.3

  Large

22.0 ± 7.4

19.0 ± 9.8

26.0 ± 18.1

3.2 ± 0.1

2.9 ± 0.3

a: Significantly different from males at the same time point (p < 0.05).

Values are mean ± SD from three rats.

- table 2: Concentration (µg eq/g tissue) of 1,2,3-trichloropropane-derived radioactivity in tissues of male B6C3F1 mice at 60 hr post-dosing

Tissue

60 mg/kg

30 mg/kg

Blood

1.1 ± 0.3

0.3 ± 0.2 a

Liver

7.8 ± 2.2

4.0 ± 0.7 a

Kidney

5.1 ± 0.6"

3.0 ± 0.5 a

Skin

1.4 ± 0.4

1.0 ± 0.2

Adipose

1.1 ±0.3

0.5 ± 0.2

Muscle

0.8 ± 0.3

0.6 ± 0.1

Brain

1.4 ± 0.1

0.3 ± 0.1 a

Spleen

0.7 ± 0.8

1.3 ± 0.3

Lungs

1.3 ± 1.1

0.8 ± 0.4 a

Heart

1.8 ± 0.2

0.4 ± 0.2

Stomach

 

  Fore

8.6 ± 1.7 a

4.6 ± 1.5

  Glandular

1.8 ± 0.5

1.1 ±0.3 a

Intestine

 

  Small

1.9 ± 0.4

0.8 ± 0.2

  Large

2.1 ± 1.8

2.2 ± 1.8

a: Significantly different from males at the same time point (p < 0.05).

Values are mean ± SD from three rats.

- table 3: Non extractable radioactivity in selected tissues of female F344 rats 24 and 60 hr after administration of 30 mg/Kg 1,2,3-trichloropropane

Tissue

24hr

60 hr

24hr

60 hr

 

ng eq nonextraciablel/ mg protein

% nonextractable

Forestomach

780 ± 120

490 ± 100

54± 18

50 ± 6

Liver

900 ± 40

620 ± 90

71± 4

83 ± 1

Kidney

980 ± 70

720 ± 40

62± 5

67 ± 5

- table 4: Distribution and excretion of 1,2,3-trichloropropane-derived radioactivity in male and female rats and male mice 60 hr after oral administration (30 mg/kg)

Tissue

Male Rats

Female Rats

Male Mice

 

% of total dose

Blood

0.6 ± 0.1

0.9 ± 0.2

0.1 ± 0.04

Liver

1.4 ± 0.2

1.2 ± 0.3

0.6 ± 0.03

Kidney

0.3 ± 0.1

0.3 ± 0.1

0.1 ± 0.01

Skin

1.1 ± 0.1

1.0 ±0.1

0.5 ± 0.1

Adipose

0.4 ± 0.1

0.6 ± 0.3

0.2 ± 0.1

Muscle

1.1 ± 0.3

1.0 ± 0.4

1.0 ± 0.2

Urine

57.1 ± 6.2

49.8 ± 4.3

64.0 ± 5.5

Feces

21.1 ± 4.9

19.4 ± 2.2

16.0 ± 6.0

CO2

17.7 ± 0.4

18.5 ± 0.6

20.2 ± 1.8

Volatiles

1.5 ± 0.5

1.4 ± 0.8

0.6 ± 0.4

Values are mean ± SD from three rats.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): low bioaccumulation potential based on study results
A toxicokinetic study was conducted administering 1,2,3-trichloropropane once via gavage to male and female F344 rats (30 mg/Kg bw) and male B6C3F1 mice (30 and 60 mg/Kg bw) .
The bioavailability via the oral route is high (close to 100 %), the metabolism is fast and the substance is excreted up to 90 % within 60 h in both species. Therefore the potential for bioaccumulation is regarded as low.
Metabolites are formed trough oxidation as well as reaction with glutathion. Thereby reactive intermediates are formed that probably react with biological molecules explaining significant amounts of non extractable radioactivity in liver, kidneys and forestomach.
Routes of excretion are equal between both sexes of rats and also male mice, while mice generally show indications for a faster metabolism of 1,2,3-trichloropropane.
These three organs are very likely the target organs of toxicity after oral exposure in both species.
Executive summary:

In the present toxicokinetic study (Mahmood (1991) 14C-labeled 1,2,3-trichloropropane was administered once via gavage to male and female F344 rats (30 mg/Kg bw) and male B6C3F1 mice (30 and 60 mg/Kg bw).

Animals were held in metabolic cages to sample urine, feces and exhaled air. At certain time points 3 animals were sacrificed to analyse the distribution of radioactivity in the blood and the different tissues. In addition in rats excretion of 1,2,3 -trichloropropane and its metabolites in the bile was examined between 0.5 and 5 h post dosing. Some of the major metabolites were identified in rat and mouse urine and rat bile via NMR and mass spectroscopy.

The bioavailability via the oral route is high (close to 100 %), the metabolism is fast and the substance is excreted up to 90 % in rats and close to 100 % in mice within 60 h. The excretion pattern is 20% via feces in both species, 50 % and 65 % via urine and 20 and 15% via exhalation rats and mice respectively. Exhalation is mainly as carbon dioxide and only minor amounts as unmetabolised 1,2,3 -trichloropropane.

Nevertheless a combined amount about 4 % of the radioactivity is found in liver, kidneys, skin, adipose tissue and muscles of rats and a total amount of about 2.5 % in male mice in these tissues 60 h after application. Therefore a low bioaccumulation potential is determined for 1,2,3 -trichloropropane.

Metabolites are formed through oxidation as well as reaction with glutathion (N-acetyl-S-(3-chloro-2-hydroxypropy1)-L-cysteine (ACPC), rat urine; S-(3 -chloro-2 -hydroxypropy1)-L-cysteine (CPC), mice urine; 2 -(S-glutathionyl)malonic acid (GMA), rat bile). Thereby reactive intermediates are formed that probably react with biological molecules explaining significant amounts of non extractable radioactivity in liver, kidneys and forestomach.

Routes of excretion are equal between both sexes of rats and also male mice, while mice generally show indications for a faster metabolism of 1,2,3-trichloropropane.

These three organs are very likely the target organs of toxicity after oral exposure in both species.