Disodium 2-hydroxyethyliminodi(acetate)

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From Nov. 11, 1985 to Nov. 21, 1985

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable study report, followed scientific principles/standards

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1985

Report date:

1985

Materials and methods

Objective of study:

absorption

distribution

excretion

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Radiolabelled test substance was administered to male CD rats at the concentration of 70 µmoles radiolabelled test substance/g for 10 days. Blood samples, urine, feces, GI wash, cage washes and organs were all assayed for their 14-C content by standard methods. The urine, plasma and plasma filtrate were assayed for their Ca, Mg and Zn levels by atomic absorption spectroscopy. The kidneys were evaluated histologically.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Disodium 2-hydroxyethyliminodi(acetate)

EC Number:

205-187-4

EC Name:

Disodium 2-hydroxyethyliminodi(acetate)

Cas Number:

135-37-5

Molecular formula:

C6H9NO5.Na2

IUPAC Name:

disodium 2-hydroxyethyliminodi(acetate)

Details on test material:

- Name of test material: 2-Hydroxyethyl imindodiacetic acid (HEIDA)
- TSIN# B0882-01
- Substance type: Pure active substance
- Physical state: Not reported

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

other: CD

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Not reported
- Age at study initiation: Not reported
- Weight at study initiation: Approx. 246g
- Housing: Animals were fitted with anal cups and housed in metabolism cages during the 10 day exposure period.
- Individual metabolism cages: Not reported
- Diet: Purina Laboratory Chow; ad libitum
- Water: Not reported
- Acclimation period: Not reported

ENVIRONMENTAL CONDITIONS: No details on environmental conditions were provided in the study report.

IN-LIFE DATES: From: Nov. 11, 1985 To: Nov. 21, 1985

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: feed

Details on exposure:

DIET PREPARATION: The 14-C test substance was mixed in ground in the Purina Laboratory Chow diet which contained 70 µmoles of test substance/g diet. Unlabeled test substance was used as a diluents.
- Rate of preparation of diet: Not reported
- Mixing appropriate amounts with: Purina Laboratory Chow
- Storage temperature of food: Not reported

HOMOGENEITY AND STABILITY OF TEST MATERIAL: Not reported

Duration and frequency of treatment / exposure:

10 days, continuously in the diet

Doses / concentrations

Remarks:

Doses / Concentrations:
70 µmoles/g diet

No. of animals per sex per dose / concentration:

5 male rats/dose

Control animals:

yes, concurrent vehicle

Positive control reference chemical:

No

Details on study design:

- Dose selection rationale: Not reported

OBSERVATIONS:
- Daily feed and water consumption records were maintained.
- The animal, urine and feces samples were weighed daily.

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Urine, feces, blood, plasma, serum or other tissues, cage washes.
- Time and frequency of sampling: Daily urine and feces samples were collected, cages were rinsed every two days with distilled water, blood and tissues were collected on the 11th day of the study.

COLLECTION AND PROCESSING OF SAMPLES
- Cages were rinsed every 2 days with distilled water and rinses were collected.
- On the morning of the 11th day, the animals were anesthetized with ether and blood was collected from vena cava in heparinized syringes. The blood was centrifuged and blood cells washed with thrice with an equal volume of saline. A portion of plasma was filtered through an Amicon PM-10 filter.
- The heart, liver, kidneys and bladder were excised and weighed. The left kidney was fixed for histological examination. The bladder was opened, everted, rinsed with distilled water and blotted before weighing.
- The gastrointestinal tract was removed and flushed with saline.
- The left femur was excised and trimmed.

DETERMINATION OF RADIOACTIVE CONCENTRATION: The blood samples, urine, feces, GI wash, cage washes and organs were all assayed for their 14C content by standard methods.

DETERMINATION OF MINERAL DISPOSITION: The urine, plasma and plasma filtrate were assayed for their Ca, Mg and Zn levels by atomic absorption spectroscopy.

HISTOLOGICAL EVALUATION: The kidneys from the controls and the treated animals were evaluated histologically.

METABOLITE CHARACTERISATION STUDIES: Not reported

TREATMENT FOR CLEAVAGE OF CONJUGATES: Not reported

Statistics:

Mean and standard deviations were calculated for the values obtained.

Results and discussion

Main ADME results

Main ADME results 1

Type:

absorption

Results:

Test substance was readily absorbed after dietary administration.

Main ADME results 2

Type:

distribution

Results:

After absorption, test substance accumulates in bones and to a much lesser extent in soft tissues

Main ADME results 3

Type:

excretion

Results:

Absorbed radioactive test substance was excreted through urine

Toxicokinetic / pharmacokinetic studies

Details on absorption:

The test substance was readily absorbed with 85% of the ingested dose voided in the urine and <10% recovered in feces.
The test substance admixed in diet attains equilibrium after only one dose.

Details on distribution in tissues:

The test substance did not accumulate in blood cells nor did it bind to plasma proteins to an appreciable extent. The plasma ultrafilitrate contained approx. 90% of the plasma total test substance.

- Of the tissues assayed the kidney had the highest concentration of 14-C test substance, followed by the bone; the liver and bladder had the same 14-C test substance concentration which was greater than that of the heart. The high kidney level probably reflects entrapment of urine in the kidney. The high bone concentration of test substance was expected since compounds that form complexes with divalent metals accumulate in bone.

Details on excretion:

Urine output (g/rat/day) was comparable between the test material group and controls, and displayed a time associated increase in both groups. In contrast, both groups displayed a time-dependent decrease in fecal output but the mass of feces excreted by the control exceeded that voided by the rats ingesting the test substance at 70 µmole/g diet.

Urine contained 86 ± 1% of the recovered 14-C test substance equivalents while the feces contained 6.5 ± 0.3%. The remainder of the recovered 14-C test substance was in the cage washes (5-11%).

The percent of the recovered 14-C test substance present in the urine did not vary during the nine days or 24 hour urine collections showing that the test substance attains equilibrium rapidly in rats.

Metabolite characterisation studies

Metabolites identified:

not measured

Any other information on results incl. tables

BODY WEIGHT:

- The test substance caused an initial decrease in body weight and then essentially no change during the 10-day period. The test substance was associated with a marked decrease in body weight with time as compared to control group.

FEED AND WATER CONSUMPTION:

- A marked decrease in diet consumption was observed in test substance-treated animals with an average intake of 14 g/day from days 4-10 when compared to the controls (22 g/day).

- The test substance consumption had a lesser effect on water consumption and increased the water/diet (mass/mass) ratio relative to the controls.

MINERAL DISPOSITION:

- The test substance consumption resulted in a marked increase in the relative excretion of Ca and Zn but it did not significantly changed Mg excretion. Overall, the test substance caused an approx. tripling of urinary divalent cations.

- The urine contained more amount of test substance than divalent minerals on a molar basis (test substance/M+2 = 2.3±0.3).

- The test substance did not affected Ca or Mg concentrations either in the total plasma or the plasma ultrafiltrate. However, a marked decrease in plasma Zn (15.2±1.0 nmoles/mL in control group vs 8.1±0.8 nmoles/mL in test substance-treated group) was observed.

- Plasma ultrafiltrate Zn was too low to measure except for 2 samples from test substance-treated animals.

ORGAN WEIGHT:

- The relative and absolute kidney weights were increased in test substance treated animals. The relative kidney weight from the rats ingesting test substance was 12.1±2.2 g/kg bw vs 7.9±0.2 g/kg bw for the control samples. The increase in kidney absolute weight occurred in spite of the lower final body weight in animals that ingested the test substance.

- Relative organs weights of heart, liver, bladder and femur were similar in control and test substance treated groups.

RENAL HISTOLOGY

- The histological evaluation of the 5 kidneys from rats ingesting 70 µmoles test substance/g diet for 10 days showed severe signs of renal damage. In addition, overt signs of renal toxicity, including renal tubular cells vacuolization with hyperplasia, were noted in each kidney exposed to test substance but not in any of the controls.

Table 1. Tissue distribution of 14C-HEIDA expressed as 14C-HEIDA equivalents/g of tissue (Study # 31690)

Organ	14C HEIDA (µmoles/g)
Kidney	7.1±1.5
Femur	2.4±0.4
Liver	1.4±0.7
Bladder	1.4±0.1
Heart	0.08±0.02
Plasma	0.36±0.12
Plasma ultrafiltrate	0.32±0.09
Blood cells	0.04±0.02

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): other: test substance was readily absorbed and mainly excreted in urine
HEIDA was readily absorbed when fed through diet to CD rats at test substance concentration of 70 µmoles/g diet. The test substance accumulated in bone and to a much lesser extent in soft tissue (i.e. heart, liver or bladder) and induced morphological and histological changes in kidney.

Executive summary:

The purpose of this study was to determine the absorption, distribution and excretion of Hydroxyethyl imidodiacetic acid when administered through diet to male CD rats. 

A total of 10 male CD rats were assigned to control and treatment groups (5/group), fitted with anal cups and housed in metabolism cages. Treatment group received 70 µmoles of 14C-labeled test substance/g in Purina Laboratory Chow diet, ad libitum for 10 days. Body weight and feed and water consumption were recorded daily. Urine and feces samples were collected daily and weighed.  The cages were rinsed every two days with distilled water. 

Animals were anesthetized with ether on the morning of 11th day and blood was collected. The heart, liver, kidneys and bladder were excised and weighed. The left kidney was fixed for histological examination. The GI tract was removed and flushed with saline. The bladder was opened, everted, rinsed with distilled water and blotted before weighing. The left femur was excised and trimmed. The blood samples, urine, feces, GI wash, cage washes and organs were all assayed for their 14C content by standard methods. The urine, plasma and plasma filtrate were assayed for their Ca, Mg and Zn levels by atomic absorption spectroscopy for the determination of mineral disposition.

 

The test substance caused an initial decrease in body weight and then essentially no change during the 10-day period. In contrast, the controls showed a linear increase in body weight with time. The test substance was associated with a marked decrease in diet consumption with an average intake of 14 g/day from Days 4-10 when compared to the controls (22 g/day). The test substance was readily absorbed with 85% of the ingested dose voided in the urine and <10% recovered in feces. Urine output (g/rat/day) was comparable in the two groups and displayed a time associated increase in both groups.  Both groups displayed a time-dependent decrease in fecal output, but the mass of feces excreted by the control exceeded that voided by the rats ingesting test substance at 70 µmoles/g diet. 

The urine contained 86±1% of the recovered 14C-test substance equivalents, while the feces contained 6.5±0.3%.  The remainder of the recovered 14C-test substance was in the cage washes (5-11%). The percent of the recovered 14C-test substance present in the urine did not vary during the nine days of 24 h urine collections showing that the test substance attained equilibrium very rapidly in rats. Of the tissues assayed, the kidney had the highest concentration of 14C-test substance followed by the bone; the liver and bladder had the same14C-test substance concentration, which was greater than that of the heart. The high kidney level probably reflected entrapment of urine in the kidney. The high bone concentration of test substance was expected since compounds that form complexes with divalent metals accumulate in bone. The bladder attained a test substance concentration similar to that in the liver. The test substance did not accumulate in blood cells, nor did it bind to plasma proteins to an appreciable extent; the plasma ultrafiltrate contained approx. 90% of the plasma total test substance.

The test substance consumption resulted in a marked increase in the relative excretion of Ca and Zn but it did not significantly change Mg excretion. Overall, the test substance caused an approx. tripling of urinary divalent cations. The urine contained more amount of test substance than divalent minerals on a molar basis (test substance/M⁺²= 2.3±0.3). The test substance did not affected Ca or Mg concentrations either in the total plasma or the plasma ultrafiltrate. In contrast, test substance ingestion was associated with marked decrease in plasma Zn. Plasma ultrafiltrate Zn was too low to measure except for 2 samples from test substance-treated animals.

The histological evaluation of the 5 kidneys from rats ingesting 70 µmoles test substance/g diet for 10 days showed severe signs of renal damage. In addition, overt signs of renal toxicity, including renal tubular cells vacuolization with hyperplasia, were noted in each kidney exposed to test substance but not in any of the controls. 

In conclusion, the test substance was readily absorbed when fed through diet to CD rats at test substance concentration of 70 µmoles/g diet. The test substance accumulated in bone and to a much lesser extent in soft tissue (i.e. heart, liver, or bladder) and induced morphological and histological changes in kidney.