2-[(2-methoxy-4-nitrophenyl)azo]-N-(2-methoxyphenyl)-3-oxobutyramide

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1984

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: well performed research study, no guideline study, no GLP

Objective of study:

other: Absorption, distribution and excretion

Principles of method if other than guideline:

investigation of absorption, distribution and excretion after a single oral application

GLP compliance:

no

Radiolabelling:

no

Species:

rat

Strain:

Fischer 344

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Portage, MI
- Age at study initiation: 7-8 weeks
- Weight at study initiation: 146-180 g
- Fasting period before study: no data
- Housing: no data
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): no data
- Water (e.g. ad libitum): no data
- Acclimation period: no data


ENVIRONMENTAL CONDITIONS: no data

Route of administration:

oral: gavage

Vehicle:

corn oil

Duration and frequency of treatment / exposure:

single exposure, investigation after 1, 4, 24 and 48 hours after dosing

Remarks:

Doses / Concentrations:
12.6 mg/kg

No. of animals per sex per dose / concentration:

3 animals per time point

Control animals:

no

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, stomach contents, intestinal contents and "various tissues"
- Time and frequency of sampling: 1, 4, 24, 48 h after dosing

Details on absorption:

The study did not find evidence of systemic absorption on Pigment Yellow 74. Small quantities of componds present in samples of tissues that were in direct contact with the substance were be attributed to mechanical adherance to the tissues rather than to absorption.

Details on distribution in tissues:

1 and 24 hours after dosing most of the administered material was present in the gut contents and none was in the faeces. 24 and 48 after dosing, most substance was in the faeces (up to 86%). Detectable amounts (>3%) were only in those tissues directly in contact with the compound. No compound was found in samples of plasma, whole blood, liver, kidney, or lungs, even after administration of doses ten times larger (data not shown).

Details on excretion:

After 48 hours, about 86% of the administered dose was excreted via the feces.

Disposition of PY 74 (values in table given represent the mean % of dose for three rats (SD in brackets)):

	Disposition
Time after dosing (h)	Gut contents	Faeces*	Tissues collected	Total
1	111 (2)	< 0.1	2.6 (0.4)	114 (2)
4	103 (1)	< 0.1	2.1 (0.3)	105 (1)**
24	25.5 (16.1)	70.4 (11.5)	0.1 (0.8)	95.9 (7.1)
48	2.1 (1.4)	85.9 (22.3)	not measured	88.2 (21.7)

* the amounts present in urine samples were included in the values for faeces, because the authors concluded that the small amounts in urine were probably due to contamination of urine by faeces

** only values for two rats in this group

Results were described by the authors as follows:

One and four hours after dosing most of the administered material was present in the gut contents and none was in the faeces. Twenty four and 48 after dosing, most substance was in the faeces. Detectable amounts were only in those tissues directly in contact with the compound. No compound was found in samples of plasma, whole blood, liver, kidney, or lungs, even after administration of doses ten times larger (data not shown).

The authors concluded that the small quantities of componds present in samples of tissues that were in direct contact with the substance can be attributed to mechanical adherance to the tissues rather than to absorption.

Recoveries of the pigment was nearly complete.

Conclusions:

Interpretation of results: other: The study did not find evidence of systemic absorption on Pigment Yellow 74.

Executive summary:

Male Fischer 344 rats received 12.6 or 126 mg/kg Pigment Yellow 74 by gavage. Twenty four and 48 hours after dosing most part of the substance was detected in the faeces (up to 86%). Only minor amounts (< 3%) were detected in tissues all of which were in direct contact with the substance, so that it can be attributed to mechanical adherance to the tissues rather than to absorption.

Description of key information

Short description of key information on bioaccumulation potential result: 
An in vivo study in rats did not find evidence of systemic absorption of Pigment Yellow 74 after a single oral administration of up to 126 mg/kg. An in vitro investigation on metabolism using rat liver and human liver microsomes and expressed human cytochrome P450s identified two phase I metabolites when Pigment Yellow 74 was added solubilized in DMSO.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

The toxicokinetic profile of a substance comprises its absorption into the body, its distribution in the body, its metabolism in the body and its excretion from the body. Taking into account the physicochemical properties and the toxicological test results, qualitative estimates for these aspects may be deduced for Pigment Yellow 74.

Absorption: a prerequisite for a relevant absorption is that the substance can be dissolved in either aqueous (e.g., gastrointestinal fluid, blood plasma, sweat) or lipophilic (e.g., lipoproteins, lipid membranes, triglycerides) media or in both. Pigment Yellow 74 can be considered insoluble because it has an extremely low solubility in water and n-octanol. Therefore, it is unlikely that Pigment Yellow 74 becomes systemically bioavailable after oral, dermal or inhalation exposure.

An in vivo study in rats did not find evidence of systemic absorption of Pigment Yellow 74 after a single oral administration of up to 126 mg/kg. In addition, the results of acute oral toxicity, acute dermal toxicity and repeated oral toxicity studies also give valuable indications with regard to absorption of the test substance. Based on the acute oral toxicity and the 90-day oral toxicity studies, which did not reveal any systemic effects that would indicate that the pigment had entered the body, no indications of significant absorption via the gastrointestinal tract has to be assumed.

Pigment Yellow 74 does not have particular skin or eye irritating or skin sensitizing properties that would imply a dermal absorptive potential.

In the unlikely event of exposure to aerosolized pigment in respirable form, the substance is considered likely to behave like an inert dust.Therefore, the deposited pigment particles will mostly be cleared from the lung via the mucocilliary transport.As the pigment will not dissolve in the lung surfactant, the only way the pigment can enter the body is via phagocytosis of pigment particles by lung macrophages followed by migration of the macrophages into the interstitium and into the draining lymph nodes. However, the internal dose delivered via this mechanism can be considered negligible.

 

Distribution: the 90-day oral repeated dose toxicity study did not indicate any relevant histopathological changes in any of the investigated organs. This may indicate that either the pigment does not affect special organs as targets, i.e., is non-toxic, or is not distributed within the body in significant amounts. As indicated above, the physico-chemical parameters of the pigment support the conclusion that the pigment is not absorbed into the body and thus does not become systemically available. There were also no other signs of deposition of the pigment in any organ including excretory organs, like the kidney, indicating that even exposure to high doses of the pigment does not lead to bioaccumulation in special compartments of the body. 

 

Metabolism: Since the dissolution of the substance in cellular fluid or cellular membranes is a prerequisite for its metabolism, it is unlikely that under usual exposure conditions the insoluble pigment becomes accessible for metabolizing systems in relevant amounts. In vitro investigation on metabolism using rat liver and human liver microsomes and expressed human cytochrome P450s identified two phase I metabolites when Pigment Yellow 74 was added solubilized in DMSO. In the mutagenicity tests, the pigment proved to be non-toxic and non-mutagenic in the absence as well as in the presence of an exogenous metabolizing system, indicating that the pigment is not converted into toxic or genotoxic metabolites. This conclusion is also supported by the lack of any consistent morphological and histopathological changes of organs involved in xenobiotic metabolism, such as the liver, in the repeated dose toxicity study.

 

Excretion: the available data indicate that Pigment Yellow 74 is not absorbed into the body. In line with this conclusion, the 90-day oral repeated dose toxicity study did not indicate morphological or histopathological effects of the pigment on organs involved in excretion of chemicals from the body, such as the kidney. There was no indication that the substance was present in the urine. Moreover, from the faeces staining observed in the single and repeated oral toxicity studies, it can be concluded that, after oral exposure, the pigment is excreted unchanged via the faeces.