[No public or meaningful name is available]

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics, other

Type of information:

other: Basic assessment using phys.-chem. properties and available toxicological data

Adequacy of study:

supporting study

Study period:

2021

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

GLP compliance:

no

Details on absorption:

Oral/gastrointestinal absorption:
The molecular weight of 1237.4 g/mol for Reactive Red 280 suggests low oral absorption. However, substances with such high molecular weights are known to get absorbed to some extent via pinocytosis and/or persorption. With the high water solubility of ≥339.7 g/L, absorption by passive diffusion may be limited by the rate at which the substance partitions out of the gastrointestinal fluid. In a 5-day range finding study, 2 Wistar rats/dose/sex were administered daily 0, 200, 600 or 1000 mg/kg bw test substance by oral gavage for a period of 5 days. Excretion of dark red faeces were noted from day 4 of treatment onwards, in animals treated at 1000 mg/kg bw/day. This was considered to be a passive effect without toxicological relevance and is commonly seen in studies where dyestuffs are administered orally. The mean body weights of the test item-treated rats were unaffected by treatment and the mean body weight gain of the test item-treated rats exceeded that of the controls. The mean testes-to-body weight ratio of the males treated with 1000 mg/kg/day was marginally lower than that of the control males. This was mainly due to the reduction noted in one of the two males at 1000 mg/kg/day although the testes-to-body weight ratio of the second male at 1000 mg/kg/day was also lower than that of the controls. The mean absolute organ weights and all other relative weights were similar to the respective control weights. No abnormal macroscopic findings were seen at any dose level.
In the 28-day repeated dose oral toxicity study, the oral administration at 50 (low dose), 200 (mid dose) and 1000 mg/kg bw/day (high dose) resulted in a secondary effect of a dose-dependent reddish discoloration of the faeces in animals of the mid and high dose groups. The occurrence of red faeces had disappeared in males and females of the high dose groups on the fourth day of the recovery period. Urinalysis indicated urine discoloration (ranging from yellow-brown to red-brown), a slight increase in pH, a moderate increase in bilirubin and a marked increase in erythrocytes in males and females of the high dose groups. At termination of the treatment-free recovery period yellow-brown urine discoloration and the increase in erythrocytes were still evident in males and females of the high dose groups. All other findings had returned to normal after discontinuation of treatment. It should be noted, that due to the test item related urine discoloration some of the changes observed in the urine may reflect artefactual changes. There was no test item-related effect on absolute organ weights noted besides of a slight decrease of -22 % (at the 5 % level) in absolute thymus weight in the high dose females. In males and females of the high dose group, relative kidney weights were increased by +17 % (at 1 % level) and +15 % (at 5 % level), respectively. In addition, in males of the mid dose group relative kidney weight was increased by +10 % (at 5 % level). Relative thymus weight was slightly decreased by -19 % (at 5 % level) in females of the mid dose group. At necropsy, a bilateral dark red discoloration of the kidneys was present in all males and females of the mid and high dose groups. A reddish discoloration of the mesenteric lymph node was noted in 4 males and 5 females of the high dose groups. A reddish discoloration at different parts of the gastro-intestinal tract was recorded in one male and 2 or 4 females of the high dose groups, whereas a reddish discoloration of the whole subcutis were recorded at necropsy in 3 high dosed females performed at the end of the treatment period. The dark red discoloration of the kidneys was still persistent in all males and females of the high dose groups at the end of the treatment-free recovery period. And the discoloration of the rectum was still noted in 3 males and 2 females of the high dose groups after the recovery period. Microscopic examination of the kidneys revealed, a minimal to moderate vacuolar tubulus cell degeneration in all main study and recovery animals of the high dose group. In addition, an increased mean grade of tubular basophilia was noted in main study females of the high dose group, as well as in the recovery males and females of the high dose group. Both changes were characterized by cells with fine-granular, red-brown pigment in cytoplasmic vacuoles. The mesenteric lymph node in main study and recovery animals of the high dose groups revealed minimal to slight amounts of foamy macrophages with fine-granular red-brown cytoplasmic pigment.

In a GLP-compliant erythrocyte micronucleus test, conducted according to OECD Guideline 474, 6 NMRI mice per sex were treated once by oral gavage with the test substance (500, 1000, 2000 mg/kg bw) dissolved in water followed by a 24 or 48 hours post exposure period. In this study, the analysis of the plasma samples of the animals treated with 2000 mg/kg bw, showed, that significant levels (38.8 - 67.7 µg/mL) of the test item could be detected in the plasma 1 hour after treatment. The level dropped to 2.1 - 4.1 µg/mL at 4 hours sampling interval. Thus, the bioavailability of the test item could be confirmed.

Taking the hydrophilic nature of Reactive Red 280 and the findings of the toxicological studies as discussed above into account, Reactive Red 280 is expected to be absorbed to some extent from the gastrointestinal tract when administered orally at substantially high doses.

Dermal absorption:
The molecular weight of 1237.4 g/mol for Reactive Red 280, indicates it being too large for dermal absorption. With high solubility in water (≥39.7 g/L) and low partition coefficient (<-5.5), dermal uptake is expected to be low for Reactive Red 280 as it is considered to be too hydrophilic to cross the lipid rich environment of the stratum corneum.
Reactive Red 280 was neither corrosive nor irritating to the skin as well as eyes, while, it was found to be sensitising to the skin. No systemic toxicity was observed in these studies.
In the acute dermal toxicity study with Reactive Red 280, neither mortality nor systemic findings were observed. No abnormalities were noted at necropsy. These findings support the assessment that low absorption is expected via dermal route.

Respiratory absorption:
Reactive Red 280 is expected to have low volatility based on the high melting point, and hence may not be available for inhalation as dust/aerosol. Further, the high water solubility (≥339.7 g/L), indicates if dust is produced, it may get trapped in the mucus and cleared via cilia. However, taking the effects observed in the oral toxicity studies with Reactive Red 280 into consideration, it may be possible that the substance will also be absorbed to some extent if it is inhaled. Nonetheless, respiratory absorption will be limited and will occur mostly at higher dosage.

Details on distribution in tissues:

The systemic distribution due to the high water solubility would most likely occur via the serum. Owing to the high molecular size and hydrophilic nature of the substance (low n-octanol/water partition coefficient and high water solubility), access of Reactive Red 280 to the central nervous system (CNS) or testes is likely to be restricted by the blood-brain and blood-testes barriers, while accumulation in body fat is unlikely to occur. As seen from the findings of the oral toxicity studies with Reactive Red 280, absorption and systemic distribution will mostly take place along the gastrointestinal tract.

Details on excretion:

The route of excretion for Reactive Red 280 has not been investigated. However, owing to the hydrophilic nature of the substance, it will be expected to be predominantly excreted via urine, while any unabsorbed remaining fraction being excreted in the faeces. In the 28-day repeated dose oral toxicity study conducted in rats at 50, 200 and 1000 mg/kg bw/day, urine discoloration (ranging from yellow-brown to red-brown) was observed in males and females of the high dose groups. At termination of the treatment-free recovery period yellow-brown urine discoloration and the increase in erythrocytes were still evident in males and females of the high dose groups. Also, a secondary effect of a dose-dependent reddish discoloration of the faeces in animals of the mid and high dose groups was also seen. The occurrence of red feces had disappeared in males and females of the high dose groups on the fourth day of the recovery period. Taking the above discussion into consideration, Reactive Red 280 can be expected to be excreted through urine for major part, while the unabsorbed dyestuff can be expected to be excreted through faeces.

Metabolites identified:

not measured

Details on metabolites:

Currently no investigation regarding metabolism of Reactive Red 280 is available. In the in vitro mammalian chromosomal aberration assay, a clastogenic effect was observed only in the presence of metabolic activation. Hence, Reactive Red 280 could be concluded to undergo some degree of hepatic metabolism, though the high water solubility of suggests that metabolism would be low and not required to facilitate the renal excretion.

Conclusions:

Reactive Red 280 would be absorbed in gastrointestinal tract at high doses, while low absorption via dermal and inhalation exposure can be expected. Systemic distribution would most likely occur via the serum, while metabolism would be limited and not required to facilitate renal excretion.

Description of key information

Due to the high water solubility and the low logP value, dermal uptake will be very unlikely and a ratio of 0.1 for oral to dermal absorption is therefore used for DNEL derivation. For the oral and inhalatory route, the default absorption values from the REACH guidance (Chapter 8, R.8.4.2) are used for DNEL derivation, namely: 100 % for inhalation, and 50 % for oral absorption.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

5

Absorption rate - inhalation (%):

100

Additional information

Absorption

Oral/gastrointestinal absorption:

The molecular weight of 1237.4 g/mol for Reactive Red 280 suggests low oral absorption. However, substances with such high molecular weights are known to get absorbed to some extent via pinocytosis and/or persorption. With the high water solubility of ≥339.7 g/L, absorption by passive diffusion may be limited by the rate at which the substance partitions out of the gastrointestinal fluid.

In a 5 day range finding study, 2 Wistar rats/dose/sex were administered daily 0, 200, 600 or 1000 mg/kg bw test substance by oral gavage for a period of 5 days. Excretion of dark red feces were noted from day 4 of treatment onwards, in animals treated at 1000 mg/kg bw/day. This was considered to be a passive effect without toxicological relevance and is commonly seen in studies where dyestuffs are administered orally. The mean body weights of the test item-treated rats were unaffected by treatment and the mean body weight gain of the test item-treated rats exceeded that of the controls. The mean testes-to-body weight ratio of the males treated with 1000 mg/kg/day was marginally lower than that of the control males. This was mainly due to the reduction noted in one of the two males at 1000 mg/kg/day although the testes-to-body weight ratio of the second male at 1000 mg/kg/day was also lower than that of the controls. The mean absolute organ weights and all other relative weights were similar to the respective control weights. No abnormal macroscopic findings were seen at any dose level. In the 28-day repeated dose oral toxicity study, the oral administration at 50 (low dose), 200 (mid dose) and 1000 mg/kg bw/day (high dose) resulted in a secondary effect of a dose-dependent reddish discoloration of the faeces in animals of the mid and high dose groups. The occurrence of red feces had disappeared in males and females of the high dose groups on the fourth day of the recovery period. Urinalysis indicated urine discoloration (ranging from yellow-brown to red-brown), a slight increase in pH, a moderate increase in bilirubin and a marked increase in erythrocytes in males and females of the high dose groups. At termination of the treatment-free recovery period yellow-brown urine discoloration and the increase in erythrocytes were still evident in males and females of the high dose groups. All other findings had returned to normal after discontinuation of treatment. It should be noted, that due to the test item related urine discoloration some of the changes observed in the urine may reflect artifactual changes. There was no test item-related effect on absolute organ weights noted besides of a slight decrease of -22 % (at the 5 % level) in absolute thymus weight in the high dose females. In males and females of the high dose group, relative kidney weights were increased by +17 % (at 1 % level) and +15 % (at 5 % level), respectively. In addition, in males of the mid dose group relative kidney weight was increased by +10 % (at 5 % level). Relative thymus weight was slightly decreased by -19 % (at 5 % level) in females of the mid dose group. At necropsy, a bilateral dark red discoloration of the kidneys was present in all males and females of the mid and high dose groups. A reddish discoloration of the mesenteric lymph node was noted in 4 males and 5 females of the high dose groups. A reddish discoloration at different parts of the gastro-intestinal tract was recorded in one male and 2 or 4 females of the high dose groups, whereas a reddish discoloration of the whole subcutis were recorded at necropsy in 3 high dosed females performed at the end of the treatment period. The dark red discoloration of the kidneys was still persistent in all males and females of the high dose groups at the end of the treatment-free recovery period. And the discoloration of the rectum was still noted in 3 males and 2 females of the high dose groups after the recovery period. Microscopic examination of the kidneys revealed, a minimal to moderate vacuolar tubulus cell degeneration in all main study and recovery animals of the high dose group. In addition, an increased mean grade of tubular basophilia was noted in main study females of the high dose group, as well as in the recovery males and females of the high dose group. Both changes were characterized by cells with fine-granular, red-brown pigment in cytoplasmic vacuoles. The mesenteric lymph node in main study and recovery animals of the high dose groups revealed minimal to slight amounts of foamy macrophages with fine-granular red-brown cytoplasmic pigment.

 

In a GLP-compliant erythrocyte micronucleus test, conducted according to OECD Guideline 474, 6 NMRI mice per sex were treated once by oral gavage with the test substance (500, 1000, 2000 mg/kg bw) dissolved in water followed by a 24 or 48 hours post exposure period. In this study, the analysis of the plasma samples of the animals treated with 2000 mg/kg bw, showed, that significant levels (38.8 - 67.7 µg/mL) of the test item could be detected in the plasma 1 hour after treatment. The level dropped to 2.1 - 4.1 µg/mL at 4 hours sampling interval. Thus, the bioavailability of the test item could be confirmed.

 

Taking the hydrophilic nature of Reactive Red 280 and the findings of the toxicological studies as discussed above into account, Reactive Red 280 is expected to be absorbed to some extent from the gastrointestinal tract when administered orally at substantially high doses.

 

Dermal absorption:

Themolecular weight of 1237.4 g/mol for Reactive Red 280, indicates it being too large for dermal absorption. With high solubility in water (≥39.7 g/L) and low partition coefficient (<-5.5),dermal uptake is expected to be low for Reactive Red 280 as it is considered to be too hydrophilic to cross the lipid rich environment of the stratum corneum. Reactive Red 280 was neither corrosive nor irritating to the skin as well as eyes, while, it was found to be sensitising to the skin. No systemic toxicity was observed in these studies. In the acute dermal toxicity study with Reactive Red 280,neither mortality nor systemic findings were observed. No abnormalities were noted at necropsy. These findings support the assessment that low absorption is expected via dermal route.

 

Respiratory absorption:

Reactive Red 280 is expected to have low volatility based on the high melting point, and hence may not be available for inhalation as dust/aerosol. Further, the high water solubility (≥339.7 g/L), indicates if dust is produced, it may get trapped in the mucus and cleared via cilia. However, taking into consideration the effects observed in the oral toxicity studies with Reactive Red 280, it can be considered possible that the substance will also be absorbed to some extent if it is inhaled. Nonetheless, respiratory absorption will be limited and will occur mostly at higher dosage.

 

Distribution

The systemic distribution due to the high water solubility would most likely occur via the serum. Owing to the high molecular size and hydrophilic nature of the substance (low n-octanol/water partition coefficient and high water solubility), access of Reactive Red 280 to the central nervous system (CNS) or testes is likely to be restricted by the blood-brain and blood-testes barriers, while accumulation in body fat is unlikely to occur. As seen from the findings of the oral toxicity studies with Reactive Red 280, absorption and systemic distribution will mostly take place along the gastrointestinal tract.

 

Metabolism

Currently no investigation regarding metabolism of Reactive Red 280 is available. In the in vitro mammalian chromosomal aberration assay, a clastogenic effect was observed only in the presence of metabolic activation. Hence, Reactive Red 280 could be concluded to undergo some degree of hepatic metabolism, though the high water solubility of suggests that metabolism would be low and not required to facilitate the renal excretion.

 

Excretion

The route of excretion for Reactive Red 280 has not been investigated. However, owing to the hydrophilic nature of the substance, it will be expected to be predominantly excreted via urine, while any unabsorbed remaining fraction being excreted in the feces. In the 28-day repeated dose oral toxicity study conducted in rats at 50, 200 and 1000 mg/kg bw/day, urine discoloration (ranging from yellow-brown to red-brown) was observed in males and females of the high dose groups. At termination of the treatment-free recovery period yellow-brown urine discoloration and the increase in erythrocytes were still evident in males and females of the high dose groups. Also, a secondary effect of a dose-dependent reddish discoloration of the faeces in animals of the mid and high dose groups was also seen. The occurrence of red feces had disappeared in males and females of the high dose groups on the fourth day of the recovery period. Taking the above discussion into consideration, Reactive Red 280 can be expected to be excreted through urine for major part, while the unabsorbed dyestuff can be expected to be excreted through faeces.

 

CONCLUSION

Based on the above discussion, it can be concluded that Reactive Red 280 would be absorbed in gastrointestinal tract at high doses, while low absorption via dermal and inhalation exposure can be expected. Systemic distribution would most likely occur via the serum, while metabolism would be limited and not required to facilitate renal excretion.