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Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2009
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Scientific publication with appropriate description of the method.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2010

Materials and methods

Objective of study:
other: placental transfer
Test guideline
Qualifier:
no guideline required
Principles of method if other than guideline:
In this study, the possibility of placental transfer of melamine and its effects on fetuses and pregnant dams were determined. Melamine was respectively administered at 0, 40 and 400 mg/kg body weight by daily gavage from gestation day (GD) 13 to GD 20 to control (C), low melamine (LM) and high melamine (HM) groups of pregnant female F344 rats. Rats were sacrificed 30 min after the last gavage.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): melamine- Analytical purity: minimum 99 %.- Producer: Wako Chemical Co. Tokyo.
Radiolabelling:
no

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
Ten- to twelve-week-old female and male F344 rats (150–200 g) were purchased from Japan SLC Inc., Shizuoka, Japan.
The rats were housed in plastic cages in a temperature and humidity-controlled room with a 12 h light/dark cycle with free access to water and food.

After an adaptation period of 1 week in the facilities, one or two female rats were housed with one male for mating. Vaginal plug check and vaginal smear observation by microscope were carried out each morning.
Day 0 of gestation (GD 0) was determined by the presence of a vaginal plug and/or spermatozoids in the vaginal smear. The female rat was then housed separately from the male and body weight (BW) was recorded daily.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
CMC (carboxymethyl cellulose)
Details on exposure:
Pregnant dams were randomly divided into three groups (six rats per group): control (C), low melamine (LM), and high melamine (HM). The doses of melamine were based on the doses used by Dobson et al. (Identification and characterization of toxicity of contaminants in pet food leading to an outbreak of renal toxicity in cats and dogs. Toxicol. Sci. 106, 251–262, 2008).
Thus, from GD 13 to GD 20, 40 mg/kg BW and 400 mg/kg BW of melamine were, respectively, administered to LM and HM groups by gavage daily.
For control rats, 1 % carboxymethylcellulose solution (Wako Chemical Co., Tokyo, Japan), used to make the melamine suspension, was administered daily.
Duration and frequency of treatment / exposure:
Gestation day GD 13 to GD 20, daily.
Doses / concentrations
Remarks:
Doses / Concentrations:
0 - 40 - 400 mg/kg bw/day.
No. of animals per sex per dose:
6 dams per group.
Control animals:
yes, concurrent vehicle
Details on dosing and sampling:
At GD 20, rats were sacrificed after isoflurane anesthetization, 30 min after the last gavage.
Blood was withdrawn from the inferior vena cava in a heparinized tube, centrifuged at 3000 g for 15 min, and the plasma was stored at -80 °C until analysis.
Amniotic fluid was sampled and the pups weighed.
Fetuses and placentas were frozen in liquid nitrogen and stored at -80 °C.
The study protocol was approved by Jichi Medical University Animal Care and Use Committee and the animals were maintained in accordance with the guidelines for the Care and Use of laboratory animals of Jichi Medical University.
Statistics:
Statistical analysis was carried out using SPSS 11.0 software. Data are expressed as mean ± SD. Pair-wise comparisons were made between melamine groups and the control group. The minimum level of probability accepted for significance was P < 0.05.

Results and discussion

Main ADME results
Type:
distribution
Results:
It appears that melamine can cross the placental barrier and its transport is dose-dependent.

Toxicokinetic / pharmacokinetic studies

Details on distribution in tissues:
Melamine was not detected in the control samples. Melamine was present in both the LM and HM plasma samples; however, the concentration in the HM group was significantly higher than in the LM group. For amniotic fluid, melamine was detected only in the HM group. Melamine was present in the fetuses of both the LM and HM groups; however, the concentration was significantly higher in the HM group than in the LM group. Melamine was detected only in the placenta of the HM. It appears that melamine can cross the placental barrier and that its transport is dose-dependent.
The Table with the results is found below.

Any other information on results incl. tables

No significant differences were observed for dam BW, number of fetuses, or fetal and placental weights between the melamine groups and the control (P > 0.05).

Melamine concentration in plasma, amniotic fluid, fetus and placenta.

Groups

Plasma (µg/ml)

Amniotic fluid (µg/ml)

Fetus (µg/g BW)

Placenta (µg/g)

C

ND

ND

ND

ND

LM

239.1 ± 39.6

ND

327.7 ± 117.0

ND

HM

1413.7 ± 146.8*

192.8 ± 30.0

570.0 ± 107.7*

1117.7 ± 304.4

Values are expressed as mean ± SD, n= 6.

C: control group, LM: low melamine group, HM: high melamine group,

ND: not detected.

*P< 0.01.

Applicant's summary and conclusion

Conclusions:
Ingested melamine passes dose-dependently the placental barrier to reach the fetus.
Executive summary:

In this study, the possibility of placental transfer of melamine and its effects on fetuses and pregnant dams were determined. Melamine was respectively administered at 0, 40 and 400 mg/kg body weight by daily gavage from gestation day (GD) 13 to GD 20 to control (C), low melamine (LM) and high melamine (HM) groups of pregnant female F344 rats. Rats were sacrificed 30 min after the last gavage. Melamine was not detected in any of the control and placental samples, or in amniotic fluid from the LM group. Plasma and fetal melamine concentrations in the HM group were significantly higher than in the LM group (P < 0.01).

These results show that ingested melamine dose-dependently passes the placental barrier to reach the fetus.