Praseodymium(III,IV) oxide

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 January 2018 to 16 August 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Objective of study:

toxicokinetics

Test guideline

Qualifier:

according to guideline

Guideline:

other: Note for Guidance on Toxicokinetics: the Assessment of Systemic Exposure in Toxicity Studies, PAB/PCD Notification No. 443

Version / remarks:

July 2, 1996

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Analysis was conducted at IDEA Consultants, Inc. under non-GLP condition.

Test material

Test material information

Constituent 1

Reference substance name:

Praseodymium(III,IV) oxide

EC Number:

234-857-9

EC Name:

Praseodymium(III,IV) oxide

Cas Number:

12037-29-5

Molecular formula:

O11Pr6

IUPAC Name:

tetrakis(λ⁴-praseodymium(4+)) dipraseodymium(3+) undecaoxidandiide

Test material form:

solid: particulate/powder

Details on test material:

- Storage conditions: Under room temperature (1 to 30 °C) in the dark and sealed container
- Actual storage temperature and storage period: - 18.7 to 22.7 °C - 16 October 2017 to 30 January 2018 (from receipt to the day of final preparation of dosing formulations)

Specific details on test material used for the study:

Lot number: REACH 0000383394

Radiolabelling:

no

Test animals

Species:

mouse

Strain:

other: CD2F1/Slc [SPF]

Details on species / strain selection:

CD2F1/Slc mice are used as the non-transgenic animals of same rodent strain of in vivo gene mutation assay. It is assumed that the observed toxicity profile in the wild-type animals reflect that observed in the transgenic animals.

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Japan SLC, Inc.
- Age at study initiation: 9 weeks of age
- Weight at study initiation: 23.3 to 29.9 g
- Housing: All animals were housed in a barrier system room of No. 7-117 [positive pressure] (W 4.8 × D 10.3 × H 2.6 m). One to three animals were housed in a plastic cage (W 18.2 × D 26.0 × H 12.8 cm) with bedding (ALPHA-dri™; lot No. 01117; Shepherd Specialty Papers). The analytical result of the bedding for contaminants was received from the manufacturer and it was confirmed that the levels of contaminants were within the acceptable limits of the Japan Experimental Animal Feed Association. The animal cages, the bedding and the feeders were replaced on Day 1 and once a week thereafter. The water bottles were replaced once every 2 or 3 days.
- Diet: ad libitum access to pellet diet
- Water: ad libitum
- Acclimation period: Upon arrival, each animal was monitored for general condition and body weight gains. During the quarantine and acclimation period (Day -7 to Day -1), the animals were observed once or more a day. The body weight of each animal was measured on the day of receipt and at the end of the quarantine and acclimation period. None of the animals showed abnormalities in their general condition or body weight gain.

ENVIRONMENTAL CONDITIONS
- Temperature: 22.6 -23.5 °C
- Humidity: 48 – 60 %
- Air changes:12 times or more/hour
- Photoperiod: 12 hours (lights on: 7:00, lights off: 19:00)

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

methylcellulose

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
- Preparation of vehicle (0.5 w/v % MC): An aqueous solution of methylcellulose 400 at 0.5 % (w/v) was used for the negative control. Methylcellulose 400 (2 or 4 g) was accurately weighed and transferred into a toppered volumetric cylinder. A small volume of warmed (approximately 80°C) water for injection was repeatedly added to dissolve it. After this solution was cooled to room temperature, it was adjusted to 400 or 800 mL with water for injection to make 0.5 w/v % solution. The prepared vehicle was stored in a refrigerator and was used within 14 days after preparation.
- Preparation of test material formulations:
Test material formulation (100 mg/mL): 10.0 g of the test material was weighed and transferred to a stoppered measuring cylinder and mixed with a small volume of vehicle. It was diluted to 100 mL with vehicle to prepare a 100 mg/mL formulation. The formulation was fully mixed by manual inversion and then stirred by magnetic stirrer until visibly homogeneous.
- Dispensing and storage of the test material formulations: Each test material formulation was divided into 8 portions (including 1 portion as reserve) for each administration under continuous stirring using a magnetic stirrer and stored in tight and light-resistant containers in a refrigerator (acceptable temperature range: 1 to 9 °C) until use. The actual temperature range was 3.6 to 7.6 °C during the storage period. The stored formulations were fully mixed by manual inversion and then stirred by a magnetic stirrer at least 30 minutes before use.
- Stability of the test material formulations: Within a concentration range of 10.0 to 200 mg/mL, the test material was confirmed to be stable and homogeneous in 0.5 % (w/v) methylcellulose 400 after storage for at least 8 days at ambient laboratory temperature and 2 to 8°C in the dark in the study [Validation of Methodologies for the Analysis of Praseodymium Oxide in Oral (Gavage) Dosing Formulations[1]]. And also, it was confirmed under non-GLP condition that the 10.0 and 100 mg/mL dosing formulations stored at 0 to 10°C were stable and homogeneous in 0.5 w/v % MC for at least 15 days.
- Analysis of test material formulations: The concentration of the test material formulation (100 mg/mL) prepared by the same method was confirmed in the previous study titled “Praseodymium (III, IV) oxide: Transgenic Mice (Muta™Mouse) Gene Mutation Assay [BSRC’s Exp. No. H927 (704-003)]”, and the results showed that the test material formulation had been appropriately prepared.

Duration and frequency of treatment / exposure:

The test material was administered to animals once daily for 14 consecutive days by using a disposable syringe with a Teflon sonde. The test material was administered from Day 8 to Day 21 alongside the gene mutation assay titled “Praseodymium (III, IV) oxide: Transgenic Mice (Muta™Mouse) Gene Mutation Assay.

Doses / concentrations

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose / concentration:

37 males

Control animals:

yes, concurrent no treatment

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: In the acute oral toxicity study male and female Sprague-Dawley (SD) rats treated with 2000 mg/kg of test material in 0.5 % (w/v) methylcellulose, no clinical signs and no changes of the body weight gain of the animals were observed. Combined repeated dose and reproduction/developmental screening study using SD rats revealed that the no observed adverse effect level (NOAEL) was 1000 mg/kg/day groups. Toxicity to mice was not observed, in the dose range-finding study [BSRC’s Exp. No. H926 (704-002)] in CD2F1/Slc mice treated with 100, 300 or 1000 mg/kg/day of test material in 0.5 w/v % MC. Therefore, a dosage of 1000 mg/kg/day was selected as the dose in the present study.
- Rationale for animal assignment: Animals were assigned to groups based on their body weights on Day -1 using LATOX-F/V5 computer system package. The weight range of animals was within the mean weight ±20 %.

Details on dosing and sampling:

DOSING ADMINISTRATION
- Before administration, the test material formulations were shaken by hand. Then, the individual dosing volumes of test material formulations were taken under continuous stirring using a magnetic stirrer for at least 30 minutes before use. The test material was administered orally by gavage according to the test guideline. The test material was administered to animals once daily for 14 consecutive days by using a disposable syringe with a Teflon sonde. The test material was administered from Day 8 to Day 21 alongside the gene mutation assay titled “Praseodymium (III, IV) oxide: Transgenic Mice (Muta™Mouse) Gene Mutation Assay.
- The dosing volume (mL) was set at 10 mL per kg body weight. The individual dosing volume (mL) was calculated on the basis of the most recent individual body weight measured.

OBSERVATIONS
- Observation of clinical signs was performed daily.
- Individual body weights of the animals in the negative control group and the test material-treated group were measured on Day -7 (day of receipt), Day -1 (day of assignment to groups), Day 7 and Day 14 (just before sampling).

TOXICOKINETIC ANALYSIS
- Analyte: Praseodymium (element) in mouse plasma
- Method of TK Sampling:
Method of blood collection: Blood was sampled from the abdominal aorta under isoflurane anaesthesia. Disposable syringes coated with heparin sodium and 23G or 25G needles were used for the blood sampling. The blood samples were transferred to polypropylene tubes and placed immediately on ice. Sampling volume: approximately 1.0 mL
Anticoagulant: Heparin sodium (1000 U/mL), 5 μL
Collection post-processing: 1) 13600 × g for 1 minute at 4 °C. 2) The upper layer (plasma) was collected, which was assumed to be a TK sample.
- Sampling point: Blood was sampled before dosing, at 1, 2, 4, and 8 hours after dosing on Day 1, and also, 1, 2, 4, and 8 hours after dosing on Day 14.
- Spare animals: Spare animals were prepared for blood collection on Day 1 and Day 14. The animals with 33 to 37 of last two digits of animal ID No. were used. When the following criteria were met, the spare animals were planned to be used, but actually were not used.
Criterion for using of spare animals:
- the blood from 4 animals was secured in each point
- moribund or dead animals were occurred
- the time of blood collecting was deviated from permissible range
- the volume of blood collected from one animal was less than 0.5 mL
- Permissible range for time of blood collecting: At 1, 2 and 4 hours after dosing: ±10 % of the scheduled time of blood collecting Before dosing and 8 hours after dosing: ±5 % of the scheduled time of blood collecting
- Storage of TK samples: Each plasma sample was identified with a label showing the experiment No., animal ID No., date and time of blood collection, and stored in a deep freezer for TK samples (acceptable range: -90 to -60 °C; actual value: -81.4 to -74.2 °C) until sending to IDEA Consultants, Inc. Since the results of the gene mutation assay titled “Praseodymium (III, IV) oxide: Transgenic Mice (Muta™Mouse) Gene Mutation Assay [BSRC’s Exp. No. H927 (704-003)]” were negative, the TK measurement was conducted using these samples according to the sponsor’s instructions.
- Handling of spare animals: All spare animals were euthanatized by CO2 inhalation after blood collection on Day 14.
- Sampling of blank plasma:
Animals: For collecting blank plasma, 23 male mice (CD2F1/Slc, 9 weeks of age) were purchased from Japan SLC, Inc.
- Method of blank plasma sampling: Blank plasma was collected according to the method described previously. On the day of animal arrival. Plasma from 3 animals was collected individually. Plasma from other animals was pooled. The blank plasma was stored in the same deep freezer as the TK samples.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Toxicokinetic parameters

Toxicokinetic parameters 1

Key result

Test no.:

#1

Toxicokinetic parameters:

Tmax: 4 hours

Remarks:

[First dose]

Toxicokinetic parameters 2

Key result

Test no.:

#1

Toxicokinetic parameters:

Cmax: 1.12 ng/mL

Remarks:

[First dose]

Toxicokinetic parameters 3

Key result

Test no.:

#1

Toxicokinetic parameters:

AUC: (0-8h) 6.45 ng.h/mL

Remarks:

[First dose]

Toxicokinetic parameters 4

Key result

Test no.:

#1

Toxicokinetic parameters:

Tmax: 1 hours

Remarks:

[Final dose (Day 14)]

Toxicokinetic parameters 5

Key result

Test no.:

#1

Toxicokinetic parameters:

Cmax: 0.94 ng/mL

Remarks:

[Final dose (Day 14)]

Toxicokinetic parameters 6

Key result

Test no.:

#1

Toxicokinetic parameters:

AUC: (0-8h) 4.16 ng.h/mL

Remarks:

[Final dose (Day 14)]

Metabolite characterisation studies

Metabolites identified:

not specified

Any other information on results incl. tables

- TK measurement:

First dose: The Tmax value for Praseodymium (element) at the dose of 1000 mg/kg was 4 hours and the Cmax value was 1.12 ng/mL. The AUC0-8h value was 6.45 ng·h/mL.

Final dose (Day 14): The Tmax value for Praseodymium (element) at the dose of 1000 mg/kg was 1 hour and the Cmax value was 0.94 ng/mL. The AUC0-8h value was 4.16 ng·h/mL.

- Body weight and general conditions: No apparent suppression of the body weight gain nor noteworthy symptom was observed.

Table 1: Concentration of Praseodymium in the mouse plasma

Sampling Point	Dose (mg/kg/day)	Concentration of Praseodymium in the plasma (ng/mL) (Mean ± S.D.)					Cmax (ng/mL)	Tmax (h)	AUC0-8h (ng.h/mL)
		Pre	1 h	2 h	4 h	8 h
First dose	Non-treatment	BLQ	-	-	-	-	-	-	-
	Vehicle	-	BLQ	BLQ	BLQ	BLQ	BLQ	-	-
	Test material 1000	-	0.41 ± 0.32	0.49 ± 0.88	1.12 ± 0.53	0.97 ± 0.57	1.12	4	6.45
Final dose (at 14 days)	Vehicle	-	BLQ	BLQ	BLQ	BLQ	BLQ	-	-
	Test material 1000	-	0.94 ± 0.59	0.59 ± 0.26	0.57 ± 0.25	0.31 ± 0.36	0.94	1	4.16

BLQ　(below limit of quantification) : <0.14 ng/mL

BLQ is assigned zero for the calculation of the mean, S.D., Cmax and AUC0-8h.

Applicant's summary and conclusion

Conclusions:

Under the conditions of this study, the results indicated that when Praseodymium (III, IV) oxide was administered to mice at the concentration of 1000 mg/kg/day, a fraction of Praseodymium was absorbed in the plasma.

Executive summary:

In order to assess systemic exposure, the test material was administered at 1000 mg/kg/day to CD2F1/Slc male mice daily for 14 days, and Praseodymium (element) in plasma at the first dose (D1) and the final dose (D14) were determined using ICP-MS. For TK analysis, blood samples were collected before dosing, at 1, 2, 4, and 8 hours after first dose, and also, 1, 2, 4, and 8 hours after final dose (at 14 days). The TK measurement was conducted at IDEA Consultants, Inc. under non-GLP condition.

At the first dose sampling point the Cmax was 1.12 ng/mL, the Tmax was 4 hours and the AUC0-8h was 6.45 ng.h/mL. At the final dose (14 days) sampling point the Cmax was 0.94 ng/mL, the Tmax was 1 hour and the AUC0-8h was 4.16 ng.h/mL.

The AUC0-8h value for Praseodymium (element) at the final dose was 0.64-fold compared to that at the first dose, and the Cmax value was also lower than that at the first dose. In the negative control group, the concentrations of Praseodymium (element) in the plasma were below the limit of quantification (<0.14 ng/mL). These results indicated that when Praseodymium (III, IV) oxide was administered to mice at the concentration of 1000 mg/kg/day, a fraction of Praseodymium was absorbed in the plasma. There were no abnormal general conditions nor apparent suppression of the body weight gain.

Under the conditions of this study, the results indicated that when Praseodymium (III, IV) oxide was administered to mice at the concentration of 1000 mg/kg/day, a fraction of Praseodymium was absorbed in the plasma.

The results of this study are considered to provide validation to the results of the TGR study (OECD TG 488, Kasamoto, 2018) written up in section 7.6.2 of this dataset.