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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: Acceptable, well-documented publication which meets basic scientific principles.

Data source

Reference
Reference Type:
publication
Title:
Comparative studies on Absorption,Distribution,and Excretion of Flame Retardants Halogenated Alkyl Phophate in Rats.
Author:
Minegishi K, Kurebayashi H, Nambaru S, Morimoto K, Takahashi T & Yamaha T
Year:
1988
Bibliographic source:
EISEI KAGAKU. 34(2): 102-114

Materials and methods

Objective of study:
absorption
distribution
excretion
Test guideline
Qualifier:
equivalent or similar to
Guideline:
EPA OPPTS 870.8223 (Pharmacokinetic Test)
Deviations:
not specified
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Radiochemical purity: >99% (ascertained by GC)
- Specific activity: 0.213 mCi/mmol
- Other: The test material was obtained from Daihachi Chemicals Indust.,Ltd.
Radiolabelling:
yes
Remarks:
C14 labeled

Test animals

Species:
rat
Strain:
Wistar
Sex:
male
Details on test animals and environmental conditions:
The 5-week-old rats weighing 150±5g were obtained from Nippon BioSupp.Center(Tokyo,Japan). Animals were kept in an environment-controlled room maintained at 22-25 centidegree and 60-70% relative humidity and artificially illuminated for 12h/d. The animals were maintained on a standard diet (MF,Oriental YEAST Co.,Ltd.) and tap water ad libitum before use. After observation of general appearance and behavior for a week, the animals were given orally dose.Each animal was housed in an alumite metabolism cage (Nihon Clea or Okazaki Sangyo Co., Ltd., Japan) to collect the urine and feces every 24h of 168h.

Administration / exposure

Route of administration:
oral: unspecified
Vehicle:
olive oil
Duration and frequency of treatment / exposure:
168 hours after single application
Doses / concentrations
Remarks:
Doses / Concentrations:
50 μmol/kg (16.38 mg/kg)
No. of animals per sex per dose:
5
Control animals:
not specified
Positive control:
not applicable
Details on study design:
no data
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled : urine, faeces, blood, plasma, serum or other tissues, cage washes, bile
- Time and frequency of sampling: Urine and faeces were collected every 24 hours for 7 days. Expired 14CO2 was determined after 72 and 96 hours. Bile was collected via cannulation every 2 hours for the first 30 hours following administration, from 30 – 46 hours and from 46 – 48 hours. Tissue samples were taken at 3, 6, 12, 24, 72 and 168 hours. Tissue radioactivity was analysed by oxidation followed by LSC and also by GC.
Statistics:
Statistical analyses of the data were carried out as reported. Analyses of distributions and recoveries of 14C-TCPP were evaluated by using Bartlett's test for homogeneity of variance, analysis of variance (ANOVA) (or Kruskal Wallis' nonparametric ANOVA when the variances were not homogeneneos), and Scheffe's multiple comparison test (or Scheffe's type mean rank test for Kruskal-Wallis'ANOVA) was used. All paired comparisons were made using Sheffe's multiple comparison test.

Results and discussion

Preliminary studies:
no data

Toxicokinetic / pharmacokinetic studies

Details on absorption:
The absorption rate is about 77% via oral route and details displayed in table 1.
Absorption was calculated from the radioisotopic measurements of cumulative urinary excretion and cumulative exhalation (performed for 3 or 4 d post-administration), and the amount in blood and tissues of rats sacrificed at 3, 6, 12, 24, 72, and 168 hr following administration.
Absorption of radiolabeled TCPP was rapid; radiolabel was detected throughout the body as early as 3 hr post-administration. At 168 hr, 75.6% of the administered oral dose had been excreted in the urine and expired air, or remained in the carcass. Another 22% was excreted in the feces; however, TCPP undergoes enterohepatic circulation (see Excretion section), and it is not clear if this proportion includes unabsorbed TCPP, TCPP excreted in the bile, or both. Therefore, at least 75.6% is absorbed following oral administration to rats.
Details on distribution in tissues:
The distribution rate was determined by the average time at which the TCPP reached the maximum concentrations in various tissues and details displayed in table 2.
The concentrations of the radiolabel in blood, heart, spleen, brain, testis, adipose tissue, and muscle were all <4 nmol/g tissue. The radiolabel concentration remained highest in the liver during subsequent timepoints up to d 7. Radiolabel reached its maximum concentration in various tissues 3–6 hr after administration.
Transfer into organs
Transfer type:
blood/brain barrier
Observation:
slight transfer
Remarks:
0.18+-0.03% after 168 h
Details on excretion:
Approximately 97% of radiolabeled TCPP (67% in urine, 22% in feces, and 7.7% in expired air) was excreted within 7 days of administration in rats. Only 0.7% of the administered dose was recovered in the carcass after 168 hr, and approximately 2.5% was not recovered. Removal of TCPP from the tissues followed a biphasic pattern. Excretion was fairly rapid from all compartments (t1/2=5.2–13.5) for the first 24 hr. During the subsequent 6 d, tissue half-lives ranged from 45 hr in the liver to 103.4 hr in adipose tissue.
Biliary radioactivity peaked within 2 hr of administration, and after 48 hr, biliary excretion represented approximately 45% of the administered dose. The ratio of biliary excretion to fecal excretion was calculated to be 2.23, suggesting to the authors that TCPP is subject to enterohepatic circulation.
Toxicokinetic parametersopen allclose all
Test no.:
#1
Toxicokinetic parameters:
half-life 1st: 16.46 in Adipose tissue
Test no.:
#2
Toxicokinetic parameters:
half-life 2nd: 103.43 in Adipose tissue

Metabolite characterisation studies

Metabolites identified:
not measured
Details on metabolites:
The metabolic transformation of TCPP has not been investigated.

Any other information on results incl. tables

Table 1 Recovery of 14C-Radioactivity from Urine, Feces and Expired Air of Rats at 168h after Oral Administration of 14C-flame Retardants

Dose % recovered
Urine f) 67.17±2.66*b,×c,×e
Feces f) 22.17±1.17
Expired air g) 7.72±0.84×a-c
Carcass f,h) 0.7±0.08*a
Total 97.76

Each flame retardant was orally administered to rats at a dose of 50 µmol/kg. Mean values are given ±S.E.

*The difference is significant, 0.01<p<0.05

×The difference is highly significant, p<0.01

a-e Superscripts show mutual differences

f five animals were used

g Three animals were used

Table 2 The Distribution of 14C-Radioactivity in the Blood and Tissues of Rats after Oral Administration of 14C-Flame Retardants

Concentration(nmol/g of tissue)
3h 6h 12h 24h 72h 168h
Tissues
Blood 3.51±0.16 4.62±0.19 2.05±0.11*a 1.46±0.12*a 0.74±0.13*a 0.26±0.04×a,*b
Heart 3.97±0.86*b 4.41±0.10 1.81±0.15*a 1.36±0.05*a 0.72±0.03*a 0.22±0.04*b
Lung 9.37±1.51*c 10.87±0.50×c 7.17±0.32×a,*b,*c 2.60±0.19*a 1.49±0.29×a 0.59±0.06*a,*b
Liver 28.64±4.38*c 31.46±1.74×c 13.69±1.43×a-c 8.00±0.56 3.30±0.86 1.15±0.26×b
Kideny 27.26±7.48 23.25±4.56*e 9.17±0.81×a,×b,*c 4.16±0.08*a 1.57±0.05 0.82±0.11*a,*b
Spleen 2.83±0.31*b,*e 4.13±0.68*e 2.20±0.18×a,×c 1.35±0.04*a 0.68±0.02 0.26±0.03*a,×b
Brain 1.2±0.14*e 2.16±0.40*c,×e 0.89±0.06×a,×c,×e 0.74±0.01 0.41±0.02 0.18±0.03×a-c
Testis 2.00±0.20 2.87±0.26 1.13±0.12 0.98±0.04*a 0.58±0.03 0.26±0.02×a,×b
Adipose 2.85±0.70 3.37±0.17*c,×e 2.10±0.11 1.51±0.04 0.95±0.02 0.54±0.03
Muscle 1.84±0.18 2.65±0.15*b,*c 1.74±0.16*a 1.02±0.03×a,×b 0.66±0.06 0.35±0.03

Each flame retardant was orally administered to rats at a dose of 50 µmol/kg. Mean values are given ±S.E.

*The difference is significant, 0.01<p<0.05

×The difference is highly significant, p<0.01

a-e Superscripts show mutual differences

f five animals were used

g Three animals were used

Table 3 The biological half life of 14C-Radioactivity in the Blood and Tissues of Rats after Oral Administration of 14C-Flame Retardants

Tissues
1 st phase b 2 nd phase c
Blood 11.67 58.73
Heart 11.23 53.72
Lung 8.65 67.94
Liver 9.68 45.89
Kideny 7.67 58.73
Spleen 11.93 61.33
Brain 13.48 70.00
Testis 5.17 74.52
Adipose 16.46 103.43
Muscle 13.38 94.93

b) Calculated from the data of 6, 12 and 24 h after dosing

c) Calculated from the data of 24, 72 and 168 h after dosing

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): no bioaccumulation potential based on study results
The concentration of radioactivity was low implying no bioaccumulation.
Executive summary:

In the comparative study on absorption, distribution, and excretion of flame retardants halogenated alkyl phosphate in rats, 5 rats were orally administered a single dose of 50 µmol/kg (16.38 mg/kg) 14C-TCPP (purity 99%; specific activity 0.213 mCi/mmol) in olive oil. Urine and faeces were collected every 24 hours for 7 days. Expired 14CO2 was determined after 72 and 96 hours. Bile was collected via cannulation every 2 hours for the first 30 hours following administration, from 30 – 46 hours and from 46 – 48 hours. Tissue samples were taken at 3, 6, 12, 24, 72 and 168 hours. Tissue radioactivity was analysed by oxidation followed by LSC and also by GC.

The recovery of radioactivity after 7 days was urine (67.2%), faeces (22.2%), expired air (7.7%) and carcass (0.7%) (total recovery was 97.8%). Seven days after oral administration of TCPP, the tissue distribution of radioactivity was, in order of decreasing concentration, liver, kidney, lung, fat, muscle, gonads, spleen, blood, heart and brain. Approximately 45% of administered radioactivity was excreted via the bile in 48 hours. This excretion was quite rapid, with approximately 30% being excreted after 3 hours. The average Tmax value for TCPP radioactivity in tissues was 5.7 hours. Tissue/blood ratios calculated at various intervals over 7 days were > 1 for liver, kidney and lung and from 12 hours in adipose tissue indicating incorporation of radioactivity into these tissues. The decrease in radioactivity in all tissues was biphasic. The longest t½ was recorded in adipose tissue in both phases of elimination (16.5 hours and 103.4 hours, respectively). However, the concentration of radioactivity was low implying no bioaccumulation. The biliary/faecal excretion ratio was 2.23 at 48 hours indicating enterohepatic re-circulation from the GI tract.