Tetrahydrothiophene 1,1-dioxide

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Objective of study:

absorption

distribution

excretion

metabolism

toxicokinetics

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Qualifier:

according to guideline

Guideline:

other: National Toxicology Program

GLP compliance:

no

Radiolabelling:

yes

Species:

mouse

Strain:

B6C3F1

Remarks:

/N

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms
- Age at study initiation: 8-10 weeks
- Weight at study initiation: 25.2-30.5 g for male mice and 18.6-21.7 g for female mice.
- Fasting period before study: not specified
- Housing: Individual metabolism cages with ability to separately collect urine, faeces and expired air.
- Individual metabolism cages: yes
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: At least one week's quarantine before initiating of the study.

ENVIRONMENTAL CONDITIONS
- Temperature: 22 ± 2 °C
- Humidity: 35-65 %
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): 12 h /12 h

IN-LIFE DATES: not specified

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
All dose formulations contained [14C]sulfolane and an appropriate amount of unlabeled sulfolane to achieve the final desired sulfolane concentration and specific activity. The target radioactivity per animal was ~ 10 μCi/rat. Oral dose formulations were prepared in water; a single dose was administered in a volume of 10 mL/kg by intragastric gavage.

Duration and frequency of treatment / exposure:

single exposure

Dose / conc.:

100 other: mg/kg bw

No. of animals per sex per dose / concentration:

1

Control animals:

no

Positive control reference chemical:

No

Details on study design:

- Dose selection rationale: Randomised
- Rationale for animal assignment: Randomised

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, plasma, cage washes,
- Time and frequency of sampling: 24 h and 48 h
- Other:
METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: urine, faeces, tissues, cage washes
- Time and frequency of sampling: 24 h and 48 h
- From how many animals: 2
- Method type(s) for identification: HPLC; LC-MS; NMR
- Limits of detection and quantification: not specified

Statistics:

Standard deviation, nothing else specified

Type:

absorption

Results:

Sulfolane was well-absorbed

Details on absorption:

In total was ≥ 89.5 % of the dose absorbed.

Details on distribution in tissues:

The total radioactivity remaining in mouse tissue was ~ 7% 24 h post administration of 100 mg/kg bw. After 48 and 72 h, the radioactivity decreased to ~ 2% regardless of administered dose. The highest detected concentrations of [14C] sulfolane were in blood, liver, lung and kidney. Higher levels observed in the bladder are likely to have occurred due to contamination from urine.

Details on excretion:

In total was 28.7 – 98.5 % of the administered dose excreted in the urine whereas 0 – 61.6% of the administered dose was excreted by the faeces.

Metabolites identified:

yes

Details on metabolites:

Treatment of urine with β-glucuronidase, sulfatase, or acylase resulted in no change to the profile, indicating that conjugates are not present. Furthermore, the presence of 3-hydroxysulfolane was confirmed in several different metabolomic tests.

Table 1. Disposition of radioactivity following a single oral of [14C]sulfolane in male and female B6C3F1/N mice

Sample	Collection Interval (h)	Male, 100 mg/kg (% of dose recovered)	Female, 100 mg/kg (% of dose recovered)
Urine	0-8	ND	1.3 ± 2.3
Urine	8-24	66.9 ± 8.4	16.4 ± 24.4
Urine	24-48	1.3 ±1.2	3.4 ± 3.7
Urine	Sub Total	68.2 ± 8.2	21.0 ± 22.4
Cage Rinse	0-8	2.6 ± 3.7	38.3 ± 34.0
Cage Rinse	8-24	13.8 ± 3.2	12.9 ± 9.6
Cage Rinse	24-48	1.8 ± 1.0	1.1 ± 1.2
Cage Rinse	Sub Total	17.6 ± 3.6	42.7 ± 27.3
Total Urine + Cage Rinse	0-72	85.8 ± 4.8	63.6 ± 34.9
Faeces	0-24	6.6 ± 4.4	30.0 ± 30.7
Faeces	24-48	1.2 ± 0.8	0.6 ± 0.5
Faeces	Sub Total	7.8 ± 4.9	30.5 ± 31.1
GI Tract Contents	-	0.01 ± 0.01	0.02 ± 0.01
Tissues	-	0.7 ± 0.0	0.6 ± 0.1
Total Dose Recovered	-	94.3 ± 0.3	94.8 ± 5.2

ND – not detected

Conclusions:

Following oral administation of 100 mg/kg bw sulfolane to mouse, ≥ 89.5 % of the dose was absorbed. Moreover, the main excretion route in male and female mouse was by the urine (86 % and 64 %) followed by the faeces (8 % and 31 %) respectively. Nevertheless, the variability was significant at different time-points. Radioactivity was observed in all examined blood and tissues where the highest concentrations were detected in blood, liver, lung, kidney, thyroid and skin.

Executive summary:

In an in vivo oral toxicokinetic study which was performed according to a similar approach as in OECD guideline 417, however, not in accordance to GLP, reported that following a single oral dose of 100 mg/kg bw sulfolane to one female and one male mouse respectively, ≥ 89.5 % of the dose was absorbed. Furthermore, the main excretion route in male mouse was by the urine (86 %) followed by the faeces (8 %). The main excretion route in female mouse was also by urine (64 %), however, more excretion had occurred in female mouse by the faeces (31 %) compared to the male mouse. Nevertheless, the variability was significant at different time-points.

Following oral ingestion of 100 mg/kg bw of the test substance in male mouse, radioactivity was observed in all examined blood and tissues where the highest concentrations were detected in blood, liver, lung, kidney, thyroid and skin. No sex differences could be identified between the two tested mice.

Reference 2

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Objective of study:

absorption

distribution

excretion

metabolism

toxicokinetics

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Qualifier:

according to guideline

Guideline:

other: National Toxicology Program

GLP compliance:

no

Radiolabelling:

yes

Species:

rat

Strain:

Sprague-Dawley

Details on species / strain selection:

Harlan Sprague-Dawley rats

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories
- Age at study initiation: 8-10 weeks
- Weight at study initiation: 207-315 g for male rats and 182-207 g for female rats.
- Fasting period before study: not specified
- Housing: Individual metabolism cages with ability to separately collect urine, faeces and expired air.
- Individual metabolism cages: yes
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: At least one week's quarantine before initiating of the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2 °C
- Humidity (%): 35-65 %
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): 12 h /12 h

IN-LIFE DATES: not specified

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
All dose formulations contained [14C]sulfolane and an appropriate amount of unlabeled sulfolane to achieve the final desired sulfolane concentration and specific activity. The target radioactivity per animal was ~ 50 μCi/rat. Oral dose formulations were prepared in water; a single dose was administered in a volume of 5 mL/kg by intragastric gavage.

Duration and frequency of treatment / exposure:

single exposure

Dose / conc.:

30 other: mg/kg bw

Dose / conc.:

100 other: mg/kg bw

Dose / conc.:

300 other: mg/kg bw

No. of animals per sex per dose / concentration:

30 mg/kg: 1 male rat 72 h exposure 100 mg/kg: 1 male and 1 female rat, 48 h & 1 male rat, 24 h; 300 mg/kg: 1 male rat, 72 h.

Control animals:

no

Positive control reference chemical:

No

Details on study design:

- Dose selection rationale: Randomised
- Rationale for animal assignment: Randomised

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, plasma, cage washes,
- Time and frequency of sampling:
24 h and 48 h
- Other:
METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: urine, faeces, tissues, cage washes
- Time and frequency of sampling:
24 h and 48 h
- From how many animals: 2
- Method type(s) for identification: HPLC; LC-MS; NMR
- Limits of detection and quantification: not specified

Statistics:

Standard deviation, nothing else is specified

Type:

absorption

Results:

Sulfolane was well-absorbed

Details on absorption:

In total was ≥ 95.5 % of the dose absorbed.

Details on distribution in tissues:

The total radioactivity remaining in male rat tissues was ~ 7% 24 hours post administration of 100 mg/kg bw. After 48 and 72 h, the radioactivity decreased to ~ 2% regardless of administered dose. The highest detected concentrations of [14C] sulfolane were in blood, liver, lung and kidney. Higher levels observed in the bladder are likely to have occurred due to contamination from urine.

Details on excretion:

In total was 83-98 % of the administered dose excreted in the urine why it became the major excretion route whereas in total 0 – 9.3 % of the administered dose was excreted by the faeces.

Metabolites identified:

yes

Details on metabolites:

Treatment of urine with β-glucuronidase, sulfatase, or acylase resulted in no change to the profile, indicating that conjugates are not present. Furthermore, the presence of 3-hydroxysulfolane was confirmed in several different metabolomic tests.

Table 1- Disposition of radioactivity following a single oral administration of [14C]sulfolane in male and female Harlan Sprague Dawley rats

 

Sample	Collection Interval (h)	Male 30 mg/kg, 72 h (% of dose recovered)	Male, 100 mg/kg, 24 h (% of dose recovered)	Male, 100 mg/kg, 48 h (% of dose recovered)	Female, 100 mg/kg, 48 h (% of dose recovered)	Male, 300 mg/kg, 72 h (% of dose recovered)
Urine	0-8	34.2 ± 3.8	11.6 ± 5.03	14.6 ± 2.9	10.1 ± 2.7	12.1 ± 2.6
Urine	8-24	50.2 ± 3.9	50.8 ± 2.74	50.0 ± 7.9	37.1 ± 7.7	43.0 ± 1.0
Urine	24-48	2.1 ± 0.5	NA	7.33 ± 3.3	6.1 ± 3.5	32.8 ± 1.6
Urine	48-72	0.2 ± 0.0	NA	NA	NA	1.6 ± 0.6
Urine	Sub Total	86.6 ± 4.9	62.4 ± 5.8	71.9 ± 4.8	53.3 ± 6.6	89.5 ± 4.4
Cage rinse	0-8	6.2 ± 3.9	9.0 ± 2.0	8.4 ± 4.1	17.0 ± 2.5	2.1 ± 0.5
Cage rinse	8-24	0.9 ±0.3	14.6 ± 7.0	10.4 ± 1.9	17.1 ± 7.8	3.2 ± 1.5
Cage rinse	24-48	0.1 ± 0.0	NA	1.7 ± 0.8	2.8 ± 0.8	0.9 ± 0.4
Cage rinse	48-72	0.3 ± 0.3	NA	NA	NA	0.3 ± 0.2
Cage rinse	Sub Total	7.5 ± 4.2	23.6 ± 6.1	20.6 ± 4.3	36. 9 ± 8.1	6.5 ± 1.9
Total Urine + Cage rinse	0-72	94.2 ± 0.9	86.0 ± 3.3	92.5 ± 1.47	90.2 ± 4.4	95.9 ± 2.8
Faeces	0-24	1.2 ± 0.5	2.8 ± 0.8	2.3 ± 0.8	3.6 ± 3.6	1.1 ± 0.4
Faeces	24-48	0.2 ± 0.1	NA	0.6 ± 0.1	1.0 ± 1.0	0.7 ± 0.1
Faeces	48-72	0.1 ± 0.1	NA	NA	NA	0.1 ± 0.1
Faeces	Sub Total	1.5 ± 0.7	2.8 ± 0.8	2.9 ± 0.8	4.6 ± 4.7	1.9 ± 0.5
GI Tract Contents	-	0.01 ± 0	0.5 ± 0.2	0.03 ± 0.0	0.04 ± 0.02	0.01 ± 0.0
Tissues	-	1.2 ± 0.1	7.2 ± 2.6	1.6 ± 0.2	1.9 ± 0.3	1.1 ± 0.1
Total Dose Recovered	-	98.1 ± 0.7	96.5 ± 0.95	97.0 ± 0.83	96.8 ± 1.02	99.8 ± 2.4

NA – not applicable

Conclusions:

Following oral ingestion of 30, 100 or 300 mg/kg bw sulfolane to rat, ≥ 95.5 % of the dose was absorbed. The test was mainly excreted by the urine in male and female rats (86.0 -95.9 %) and to a very low degree in the faeces (0.01 -0.5 %). The excretion occurred rapidly since 60 %, 82 % and 91 % of the dose recovered in urine occurred by 24 h without any intra-differences between the sexes at 100 mg/kg bw.

Executive summary:

In an in vivo oral toxicokinetic study which was performed according to a similar approach as in OECD guideline 417, however, not in accordance to GLP, reported that following a single oral dose of 30, 100 or 300 mg/kg bw sulfolane respectively, sulfolane was absorbed ≥ 95.5 %. Moreover, the mainly excretion route occurred by the urine in male and female rats (86.0 -95.9 %) and to a very low degree in the faeces (0.01 -0.5 %). The excretion occurred rapidly following oral administration of 100 mg/kg bw since 60 %, 82 % and 91 % of the dose recovered in urine occurred by 24 h without any intra-differences between the sexes.

Following oral ingestion of 100 mg/kg bw of the test substance in male rats, radioactivity was observed in all examined tissue where the concentration increased with the dose. The total radioactivity that remained in the tissues at 24 h were 7 %, however, at 48 and 72 h, the radioactivity in the tissues had decreased to < 2 % regardless of administered dose. Moreover, the highest concentrations were found in blood as well as in liver, lung and kidney.

Reference 3

Endpoint:

dermal absorption in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 417

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 427 (Skin Absorption: In Vivo Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: National Toxicology Program

GLP compliance:

no

Radiolabelling:

yes

Remarks:

[2,5-14C]sulfolane (14[C]sulfolane, 58.2 mCi/mmol)

Species:

mouse

Strain:

B6C3F1

Remarks:

/N

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms
- Age at study initiation: 8-10 weeks
- Weight at study initiation: 25.2-30.5 g for male mice and 18.6-21.7 g for female mice
- Fasting period before study: not specified
- Housing: Individual metabolism cages with ability to separately collect urine, faeces and expired air.
- Individual metabolism cages: yes
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: At least one week's quarantine before initiating of the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2 °C
- Humidity (%): 35-65 %
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): 12 h /12 h

IN-LIFE DATES: not specified

Type of coverage:

other: A metal mesh tissue capsule (placed immediately after dose administration) was used to protect the dose site from grooming.

Vehicle:

ethanol

Duration of exposure:

48 hours

Doses:

- Actual doses: 100 mg/kg bw

No. of animals per group:

2

Control animals:

no

Details on study design:

DOSE PREPARATION
- Method for preparation of dose suspensions: Approximately 24 h prior to dermal dosing, each mouse was anesthetized with isoflurane.
- Method of storage: not specified

APPLICATION OF DOSE:

VEHICLE
- Justification for use and choice of vehicle (if other than water): not specified
- Amount(s) applied (volume or weight with unit): not specified
- Concentration (if solution): 95 %
- Lot/batch no.: not specified
- Purity: not specified

TEST SITE
- Preparation of test site: Fur was clipped from each animal’s back and wiped with water. Following the cleaning, examination for nicks were performed and an outline of the dose area, 1 cm2 (1 x 1 cm), was inscribed on backs of each animal with a permanent-type felt tip marker. A single dose was applied to the dose area in a volume of 1 mL/kg using a syringe with a ball tipped feeding needle and spread evenly over the dose site.
- Area of exposure: on the back of the animal
- % coverage: not specified but an area of 1 cm2 (1 x 1 cm)
- Type of cover / wrap if used: immediately after the application of the test material, a metal mesh tissue capsule was placed to protect the dose site.
- Time intervals for shavings or clipplings: not specified

SITE PROTECTION / USE OF RESTRAINERS FOR PREVENTING INGESTION: n/a

REMOVAL OF TEST SUBSTANCE
- Removal of protecting device: following termination and blood collection, the metal appliance was removed with acetone to enable that cyanoacrylate adhesive (which were used to secure the metal appliances) was dissloved properly.
- Washing procedures and type of cleansing agent: acetone
- Time after start of exposure: 48 hours

SAMPLE COLLECTION
- Collection of blood: yes
- Collection of urine and faeces: yes
- Collection of expired air: yes
- Terminal procedure: the animals were euthanized by asphyxiation with CO2 and blood was collected via cardiac puncture and added to tubes containing K2EDTA.
- Analysis of organs: liver, kidney, heart, lung, spleen, brain, bladder, thyroid, pancreas, testes or uterus and ovaries, small intestine, large intestine, cecum and stomach (all gastrointestinal (GI) tract tissues were collected without contents) and samples of muscle (hind leg), abdominal skin and adipose (perirenal).

SAMPLE PREPARATION
- Storage procedure: All samples were stored at -20 °C until analysis.
- Preparation details: The GI tract tissues were rinsed with deionized water and the rinsate was collected separately. Tissues were divided into 2-4 aliquots (depending on tissue weight) and weighed. Liver was minced and 4 aliquots were weighed for analysis. GI tract tissues, GI contents, skin, and carcass were digested in 2N ethanolic NaOH. Triplicate faeces and tissue aliquots were digested in Soluene®-350; after digestion, samples (requiring bleaching) were decolorized with 70% perchloric acid and hydrogen peroxide. Triplicate aliquots of GI tract tissue, GI contents, skin and tissues digests and duplicate aliquots of urine, VOC and CO2 trapping solutions, plasma, cage rinse, and GI tract rinsates were added to vials containing Ultima Gold™ scintillation cocktail. All samples were analysed for radioactivity content.

ANALYSIS
- Method type(s) for identification: HPLC; LC-MS; NMR
- Liquid scintillation counting results (cpm) converted to dpm as follows: not specified
- Validation of analytical procedure: not specified
- Limits of detection and quantification: not specified

Signs and symptoms of toxicity:

not specified

Dermal irritation:

not specified

Absorption in different matrices:

In total was ≥ 63.5 % of the dose absorbed.

Total recovery:

The total dose recovered was between 63.5 – 87.3 % in mouse following dermal application of the test substance.

Table 1 - Disposition of radioactivity following a single dermal application of 100 mg/kg

[¹⁴C]sulfolane in male and female B6C3F1/N mice

Sample	Collective Interval (h)	Male - Percent of dose recovered	Female – Percent of Dose Recovered
Urine	0-8	No sample	No Sample
Urine	8-24	25.9 ±17.3	17.0 ± 8.0
Urine	24-48	3.18 ± 2.0	2.7 ± 1.6
Urine	Sub Total	43.7 ± 20.2	19.7 ± 9.6
Cage rinse	0-8	11.1 ± 2.6	32.1 ± 15.4
Cage rinse	8-24	5.8 ± 4.1	12.7 ± 8.0
Cage rinse	24-48	1.4 ± 0.8	4.9 ± 2.9
Cage rinse	Sub Total	18.3 ± 6.9	49.7 ± 9.6
Total Urine + Cage Rinse	0-48	62.0 ± 16.8	69.4 ± 2.0
Faeces	0-24	6.2 ± 5.5	7.8 ± 4.6
Faeces	24-48	1.2 ± 1.0	1.5 ± 0.9
Faeces	Sub Total	7.4 ± 6.5	9.4 ± 5.1
GI Tract Contents	-	0.02 ± 0.01	0.04 ± 0.02
Tissues	-	0.8 ± 0.3	1.7 ± 1.5
Total Absorbed Dose	-	70.2 ± 12.0	80.4 ± 3.5
Dose Site Skin	-	1.4 ± 1.4	0.9 ± 0.6
Gauze	-	1.2 ± 0.9	1.1 ± 0.7
Dermal Appliance	-	2.6 ± 3.1	1.4 ± 1.1
Dose Site Skin Rinse	-	0.1 ± 0.1	0.2 ± 0.1
Total Unabsorbed Dose	-	3.9 ± 2.9	2.7 ± 1.9
Total Dose Recovered	-	75.5 ± 11.8	84.0 ± 2.3

Conclusions:

Following dermal application of 100 mg/kg bw of sulfolane to mice, 70 % and 80 % of the applied dose was absorbed to male and female respectively. The total recovered dose recovered in males and females were 76 % and 84 % respectively.

Executive summary:

In an in vivo dermal absorption study which was performed according to a similar approach as described in the OECD guideline 427, however, not in accordance to GLP, reported that following dermal application of 100 mg/kg bw of sulfolane to the back, ≥ 63.5 % was absorbed in male and female mice respectively. The majority of the recovered dose were in the urine (62 % / 70 %); faeces (7 % / 9 % and tissue (<1 % / 2 %) to male and female respectively. The total recovered dose recovered in males and females were between 63.5 – 87.3 %.

Reference 4

Endpoint:

dermal absorption in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 417

Deviations:

not specified

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 427 (Skin Absorption: In Vivo Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: National Toxicology Program

GLP compliance:

no

Radiolabelling:

yes

Remarks:

[2,5-14C]sulfolane (14[C]sulfolane, 58.2 mCi/mmol)

Species:

rat

Strain:

Sprague-Dawley

Remarks:

Harlan

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories
- Age at study initiation: 8-10 weeks
- Weight at study initiation: 207-315 g for male rats and 182-207 g in female rats.
- Fasting period before study: not specified
- Housing: Individual metabolism cages with ability to separately collect urine, faeces and expired air.
- Individual metabolism cages: yes
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: At least one week's quarantine before initiating of the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2 °C
- Humidity (%): 35-65 %
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): 12 h /12 h

IN-LIFE DATES: not specified

Type of coverage:

occlusive

Remarks:

1 male rat and 1 female rat had covered dose sites and 1 male rat had uncovered dose site.

Vehicle:

ethanol

Duration of exposure:

48 hours

Doses:

- Actual doses: 100 mg/kg bw

No. of animals per group:

3

Control animals:

no

Details on study design:

DOSE PREPARATION
- Method for preparation of dose suspensions: substance was dissolved in 95 % ethanol.
- Method of storage: not specified

APPLICATION OF DOSE:
Approximately 24 h prior to dermal dosing, each rat was anesthetized with an intramuscular injection of 7:1 ketamine:xylazine (60 mg/kg).

VEHICLE
- Justification for use and choice of vehicle: not specified
- Amount(s) applied: not specified
- Concentration: 95 %
- Lot/batch no. (if required): not specified
- Purity: not specified

TEST SITE
- Preparation of test site: Fur was clipped from each animal’s back and wiped with gauze soaked with water, dried and examined for nicks. An outline of the dose area, 4 cm2 (2 x 2 cm), was inscribed on backs of each animal with a permanent-type felt tip marker. A single dose was applied to the dose area in a volume of 0.5 mL/kg using a syringe with a ball tipped feeding needle and spread evenly over the dose site.
- Area of exposure: on the back of the animal
- % coverage: not specified but an area of 4 cm2 (2 x 2 cm)
- Type of cover / wrap if used: Foam appliances (placed prior to dose administration) with cloth covers were used to protect the dose site of rats from grooming, with the exception of the dose group with uncovered dose site.
- Time intervals for shavings or clipplings: not specified

SITE PROTECTION / USE OF RESTRAINERS FOR PREVENTING INGESTION: n/a

REMOVAL OF TEST SUBSTANCE
- Removal of protecting device: following termination and blood collection, protective appliance was removed.
- Washing procedures and type of cleansing agent: ethanol
- Time after start of exposure: 48 hours

SAMPLE COLLECTION
- Collection of blood: yes
- Collection of urine and faeces: yes
- Collection of expired air: yes
- Terminal procedure: the animals were euthanized by asphyxiation with CO2 and blood was collected via cardiac puncture and added to tubes containing K2EDTA.
- Analysis of organs: liver, kidney, heart, lung, spleen, brain, bladder, thyroid, pancreas, testes or uterus and ovaries, small intestine, large intestine, cecum and stomach (all gastrointestinal (GI) tract tissues were collected without contents) and samples of muscle (hind leg), abdominal skin and adipose (perirenal).

SAMPLE PREPARATION
- Storage procedure: All samples were stored at -20 °C until analysis.
- Preparation details: The GI tract tissues were rinsed with deionized water and the rinsate was collected separately. Tissues were divided into 2-4 aliquots (depending on tissue weight) and weighed. Liver was minced and 4 aliquots were weighed for analysis. GI tract tissues, GI contents, skin, and carcass were digested in 2N ethanolic NaOH. Triplicate faeces and tissue aliquots were digested in Soluene®-350; after digestion, samples (requiring bleaching) were decolorized with 70% perchloric acid and hydrogen peroxide. Triplicate aliquots of GI tract tissue, GI contents, skin and tissues digests and duplicate aliquots of urine, VOC and CO2 trapping solutions, plasma, cage rinse, and GI tract rinsates were added to vials containing Ultima Gold™ scintillation cocktail. All samples were analysed for radioactivity content.

ANALYSIS
- Method type(s) for identification: HPLC; LC-MS; NMR
- Liquid scintillation counting results (cpm) converted to dpm as follows: not specified
- Validation of analytical procedure: not specified
- Limits of detection and quantification: not specified

Signs and symptoms of toxicity:

not specified

Dermal irritation:

not specified

Absorption in different matrices:

In total, ≥ 57.5 % of the applied dose was absorbed.

Total recovery:

The total dose recovered was between 57.8 – 88.0 % in rats following dermal application of the test substance.

Table 1 - Disposition of radioactivity following a single dermal application of 100 mg/kg

[¹⁴C]sulfolane in male and female Harlan Sprague Dawley rats.

Sample	Collection interval (h)	Covered Dose Site Male (% of dose recovered)	Uncovered Dose Site Male (% of dose recovered)	Covered Dose Site Female (% of dose recovered)
Urine	0-8	0.2 ± 0.1	1.5 ± 1.1	0.4 ± 0.4
Urine	8-24	3.4 ± 1.5	28.6 ± 6.5	3.7 ± 0.7
Urine	24-48	5.5 ± 1.7	10.7 ± 3.0	5.2 ± 0.9
Urine	Sub total	9.1 ± 3.2	40.8 ± 8.4	9.2 ± 1.3
Cage rinse	0-8	0.4 ± 0.2	2.9 ± 1.2	0.5 ± 0.5
Cage rinse	8-24	1.3 ± 0.6	6.6 ± 2.8	2.4 ± 1.1
Cage rinse	24-48	2.3 ± 0.6	3.3 ± 1.6	4.2 ± 4.1
Cage rinse	Sub Total	4.0 ± 1.3	12.8 ± 4.3	7.2 ± 4.8
Total Urine + Cage Rinse	0-48	13.1 ± 3.0	53.6 ± 4.1	16.4 ± 4.8
Faeces	0-24	0.1 ± 0.1	1.7 ± 0.5	0.23 ± 0.2
Faeces	24-48	0.3 ± 0.1	0.6 ± 0.1	0.5 ± 0.5
Faeces	Sub Total	0.4 ± 0.1	2.2 ± 0.6	0.7 ± 0.7
GI tract Contents	-	0.1 ± 0.0	0.1 ± 0.0	0.1 ± 0.0
Tissues	-	2.2 ± 0.3	3.3 ± 1.7	2.0 ± 1.0
Total absorbed dose	-	15.8 ± 3.5	59.2 ± 5.1	18.7 ± 6.1
Dose Site Skin	-	4.9 ± 1.0	1.6 ± 1.0	2.6 ± 1.5
Gauze	-	3.1 ± 1.1	0.4 ± 0.5	0.9 ± 0.3
Dermal appliance	-	46.7 ± 6.9	NA	59.3 ± 6.0
Dose Site Skin Rinse	-	14.6 ± 8.7	0.1 ± 0.2	2.5 ± 3.8
Total unabsorbed Dose	-	64.4 ± 4.1	0.6 ± 0.7	62.7 ± 4.1
Total Dose Recovered	-	85.0 ± 2.9	61.4 ± 3.6	84.0 ± 4.0

 

 

Conclusions:

Following dermal application of 100 mg/kg bw of sulfolane to rat, 16 and 19 % of the applied dose (covered dose site) (equivalent to 4.71 mg and 3.67 mg respectively) were absorbed in male and female rats. When the application site was uncovered, the absorption increased to approximately 60 % which probably depends on grooming/oral ingestion.

Executive summary:

In an in vivo dermal absorption study which was performed according to a similar approach as described in the OECD guideline 427, however, not in accordance to GLP, reported that following dermal application of 100 mg/kg bw of sulfolane, 16 and 19 % of the applied dose (covered dose site) (equivalent to 4.71 mg and 3.67 mg respectively) were absorbed in male and female rats respectively. When the application site was uncovered, the absorption increased to approximately 60 % which probably depends on grooming/oral ingestion. Moreover, the majority of the applied dose was recovered as unabsorbed at the dermal application site (47-59 %) as well as at the site where the skin was washed (3-18%). Furthermore, 85 % of the dose was recovered when the dose site was covered in a male rat; 61.4 % was recovered when the dose site was uncovered in a male rat and 84 % was recovered when covering the dose site in a female rat. 

Description of key information

A report on toxicokinetics of sulfolane in rats and mice following oral and dermal administration has been published by Waidyanatha et al., (2019). The study was conducted to the National Toxicology Program protocol but not in compliance with GLP. The protocol was similar to OECD test guidelines 417 and 427.

Following oral gavage administration of a single dose (100 mg/kg bw) of ¹⁴C-sulfolane to male mice, 86% of the administered dose was excreted via urine and 8% via faeces. In female mice, a lower percentage (64%) was excreted in the urine and a higher percentage (31%) in the faeces. Nevertheless, the variability was significant at different timepoints. Moreover, radioactivity could be detected in all examined blood and tissues, including liver, lung, kidney, thryoid and skin (Waidyanatha et al., 2019).

Following a single oral gavage administration of ¹⁴C-sulfolane at doses of 30, 100 or 300 mg/kg bw to male and female rats, the test material was mainly excreted via urine in male and female rats (86.0-95.9%) and to a very low degree in the faeces (0.01-0.5%). The excretion occurred rapidly since 60%, 82% and 91% (respectively) of the dose was recovered in urine by 24 hours without any differences between males and females. Following oral gavage administration of 100 mg/kg bw of sulfolane to male rats, radioactivity was observed in all examined tissue where the concentration increased with the dose. The total radioactivity that remained in the tissues at 24 hours was 7 %; however, at 48 and 72 h, the radioactivity in the tissues had decreased to <2% regardless of administered dose. Moreover, the highest concentrations were found in blood as well as in liver, lung and kidney (Waidyanatha et al., 2019).

For the purpose of deriving realistic DNELs the oral absorption of sulfolane in humans is assumed to be 100 %.

Following dermal application of 100 mg/kg bw of sulfolane to male and female rats, 16 and 19%, respectively, of the applied dose (covered dose site) (equivalent to 4.71 mg and 3.67 mg, respectively) was absorbed. When the application site was uncovered, the absorption increased to approximately 60% which was probably due to grooming/oral ingestion. Moreover, the majority of the applied dose was recovered as unabsorbed at the dermal application site (47-59%) as well as at the site where the skin was washed (3-18%). Furthermore, 85% and 84% of the dose was recovered when the dose site was covered in a male and female rat, respectively; 61.4% was recovered when the dose site was uncovered in a male rat (Waidyanatha et al., 2019).

Following dermal application of 100 mg/kg bw of sulfolane to the back of mice, 70% and 80% was absorbed to male and female respectively. The majority of the recovered dose was in the urine (62% / 70%), faeces (7% / 9%) and tissue (< 1% / 2%) to male and female, respectively. The total recovered dose recovered in males and females were 76% and 84% respectively (Waidyanatha et al., 2019).

The variation between rat and mouse demonstrates a species difference in dermal absorption of sulfolane; the higher absorption in mice is concluded to occur due to their lower skin thickness; the skin thickness of mice is approximately 0.70 mm compared to approximately 2.09 mm for rats (June and Maibach, 2015 as cited in Waidyanatha et al., 2019). Several papers have concluded that human skin is more structurally similar to the rat skin than mouse skin, but is also slightly thicker (approximately 2.97 mm). Humans have a stratum corneum of 16.8 μm; epidermis of 46.9 μm and whole skin of 2.97 mm whereas rats have a stratum corneum of 18 μm; epidermis 32 μm and whole skin of 2.09 mm (June and Maibach, 2015 as cited in Waidyanatha et al., 2019). Therefore, it is reasonable to conclude that dermal absorption of sulfolane in humans will occur to a similar or lower extent than in rats (Waidyanatha et al., 2019).

Consequently, for the purpose of deriving realistic DNELs the overall dermal absorption for humans is assumed to be 20 % (conservative value based on dermal absorption of 16 -19 % in rats).

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

20

Additional information

The urinary excretion of unmetabolized sulfolane was studied in male Sprague-Dawley rats from a single intravenous injection of 500 or 1,000 mg/kg sulfolane (Andersen et al., 1976). The proportion of dose excreted unchanged increased as the dosage was increased. In a separate set of experiments, the elimination of sulfolane from the blood was determined in a rabbit, dog and squirrel monkey following a single intravenous doses of sulfolane. Sulfolane was rapidly distributed with volumes of distribution of about 1.0 L/kg; the elimination half-life was 3.5 to 5 hours. 

Andersen, M.E., Jones, R.A., Kurlansik, L., Mehl, R.G., and Jenkins, L.J., Jr. (1976) Sulfolane-induced convulsions in rodents. Res. Commun. Chem. Pathol. Pharmacol. 15: 571-580.

[35S]-Sulfolane (100 mg) was injected intraperitoneally into three male Wistar rats and the 24-hour urinary samples were analysed (Roberts and Warwick, 1961). One major metabolite was excreted, constituting at least 85% of the urinary radioactivity. It was identified as 3-hydroxysulfolane. 

Roberts, J.J., and Warwick, G.P. (1961) The mode of action of alkylating agents – III The formation of 3-hydroxytetrahydrothiophene-1;1-dioxide from 1:4-dimethylsulphonyloxybutane (Myleran), S-β-L-alanyltetrahydrothiophenium mesylate, tetrahydrothiophene and tetrahydrothiophene-1:1-dioxide in the rat, rabbit and mouse. Biochem. Pharmacol. 6: 217-227.