Registration Dossier

Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study was conducted prior to the introduction of Good Laboratory Practices. The study was conducted according to acceptable scientific standard methods which were used in the test laboratory at the time the study was conducted.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1978
Report Date:
1978

Materials and methods

Objective of study:
metabolism
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Groups of 4 male or 4 female rats were dosed by gavage with either 40 or 400 mg/kg bw of [14]C 1,4-cyclohexanedimethanol and placed in metabolism cages for 48 hours. Urine, feces, expired air, and cage washings were collected throughout the experiment and analyzed for radioactivity. Urine was treated under a variety of conditions to characterize and identify metabolites. Other groups of 3-4 male rats were administered 400 mg/kg bw of non-radioactive CHDM by gavage and blood samples were removed at 0.25, 1.0, 1.5, 2, 3, and 4 hours after dosing to determine the half-life of CHDM in blood.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Type:
Constituent
Details on test material:
-Radioactive test substance as purchased: [Methylol-[14]C] 1, 4-cyclohexanedimethanol
-Source: New England Nuclear, Boston, MA
-Composition as purchased: isomeric mixture of 70% cis- and 30% trans-CHDM
-Specific activity: 7.55 µC/mg
-Purity: >98%

-Radioactive test substance used for dosing: [14]C CHDM isomers were separated by gas chromatography using a thermal conductivity detector and a trapping device; each separated isomer had a purity of >95% when measured by gas chromatography with flame ionization detector. The isomers were combined in a 70% trans-and 30% cis-isomer mixture (to conform with the non-labeled CHDM-R sold by Eastman Organic Chemicals).

-Non-radioactive CHDM used for dosing: mixture of 70% trans- and 30% cis-isomers
-Source: Eastman Organic Chemicals, Rochester, NY
Radiolabelling:
yes

Test animals

Species:
rat
Strain:
other: Charles River CD-COBS rats
Sex:
male/female
Details on test animals and environmental conditions:
-Strain: Charles River CD-COBS rats (Wilmington, MA)
-Body weight (at study start): 200-300 g
-Feed: Purina rat chow; animals were fasted overnight before dosing
-Water: ad libitum
-Housing for metabolic fate portion of study: after administration of radiolabeled test substance, animals were housed in Delmar-Roth glass metabolism cages for 48 hours; dehumidified air was drawn through the cages at about 500 mL/min.
-Housing during determination of CHDM half-life (T1/2) in blood: no information was provided on housing conditions for male rats dosed with non-radiolabeled material.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
Metabolic fate phase of the study:
After the separated radioactive CHDM isomers had been recombined in a 70% trans- and 30% cis-ratio, the mixture was diluted with carrier, dissolved in water, and administered as a single dose by gastric intubation to groups of 4 male or 4 female rats. Rats were fasted overnight before dosing.

Determination of half-life phase of the study:
Groups of 3-4 male rats received a single 400 mg/kg bw dose of non-radioactive CHDM by gastric intubation.
Duration and frequency of treatment / exposure:
Metabolic fate phase: Rats received a single dose of [14]C-CHDM and were observed for 48 hours.

Half-life phase: Rats received a single dose of CHDM and blood was collected for up to 4 hours.
Doses / concentrations
Remarks:
Doses / Concentrations:
Metabolic fate phase: Male rats were given either 40 or 400 mg/kg bw [14]C-CHDM while females were dosed with 400 mg/kg bw [14]C-CHDM. Each rat received between 1.1-4.5 µCi of radioactivity.

Half-life phase: Male rats were dosed with 400 mg/kg bw of non-radioactive CHDM.
No. of animals per sex per dose:
Male 40 mg/kg bw [14]C-CHDM: 4 rats
Male 400 mg/kg bw [14]C-CHDM: 4 rats
Female 400 mg/kg bw [14]C-CHDM: 4 rats
Male 400 mg/kg bw CHDM: 30 rats
Control animals:
no
Positive control:
no
Details on dosing and sampling:
METABOLIC FATE PHASE: After receiving a single dose of [14C]CHDM, rats were placed into individual metabolism cages designed for the efficient collection of urine, feces and expired air. Urine was collected at 4, 8, 12, 24, and 48 hours after dosing and feces were collected at the end of the study. Dehumidified air was drawn through the metabolism cages at 500 mL/min and respiratory CO2 was trapped in two gas washing bottles connected in series containing a 2:1 (v/v) 2-methoxyethanol:2-aminoethanol solution that was changed daily. Metabolism cages were cleaned with water and ethanol at the end of the study. After 48 hours, animals were euthanized and select organs were harvested. Carcasses were retained for analysis and all samples were analyzed for radioactivity.

Radioactivity Assays:
Feces and tissues (brain, heart, lung, kidney, fat, and liver) were extracted in 95% aqueous acetone; carcasses were homogenized and extracted with 95% aqueous acetone followed by n-hexane. Extracts were counted in Ready-to-Use II. Feces, tissues, and carcass residues were dried, powdered, combusted, and counted. The cage washes were filtered and the residues extracted in 95% aqueous acetone; filtrates and extracts were counted in Ready-to-Use II and the residues were dried, powdered, combusted, and counted.

Urine was pooled for the first 24 hours from each rat; a 5 mL sample was adjusted to pH 1 and extracted continuously for 18 hours with diethyl ether to remove unconjugated acidic metabolites. The extracts were evaporated to dryness, derivatized with N,O-Bis(trimethylsilyl)acetamide (BSA) and then analyzed and separated by flame ionization gas chromatography. Samples were also analyzed by gas chromatography-mass spectrometry (GC-MS). After ether extraction, the aqueous portions were (a) treated with equal volumes of 6N HCL or 12N HCl, heated for 30 min at 90 °C, and then extracted with diethyl ether for 18 hrs; or (b) adjusted to pH 5, treated with an equal volume of beta-glucuronidase in acetate buffer, heated to 37 °C for 18 hr, acidified, and then extracted for 18 hr with diethyl ether. Aqueous phases remaining after ether extractions were counted with Ready-to-Use II.

A Tri-Carb Model 3375 liquid scintillation spectrometer (Packard Instrument Co., Inc, Downers Grove, IL) was used for sample counting. Samples were counted in either a toluene-based scintillator or Eastman Ready-to-Use II (Eastman Organic Chemicals, Rochester, NY). A Packard Model 306 sample oxidizer was used for the combustion of feces, tissues, and carcasses.

BLOOD PARTITION COEFFICIENT:
Whole blood was removed from an untreated rat by cardiac puncture, heparinized, and [14]C-CHDM was added. After mixing and centrifugation, plasma was decanted and red blood cells washed with saline. Plasma and saline washes were pooled and counted in Ready-to-Use II.

HALF-LIFE OF CHDM IN BLOOD:
Groups of 3-4 male rats were dosed with 400 mg/kg bw CHDM by gavage. Blood was removed at 0.25, 1, 1.5, 2, 3, and 4 hours after dosing; heparinized blood was separated by centrifugation, and plasma extracted with diethyl ether. Extracts were analyzed for CHDM by flame ionization gas chromatography and GC-MS.
Statistics:
No statistical analysis was performed on this study.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:
When adult male and female rats were administered a single oral dose of approximately 40 or 400 mg/kg bw [14]C-CHDM, the test material was rapidly absorbed from the gut. Approximately 89-97% of the administered radioactivity was recovered in the urine, 1-3% in the feces, 1-7% in the cage washings, and 0.1-0.05% in expired air within 48 hr of dosing.
Details on distribution in tissues:
Radioactivity remaining in the carcasses accounted for less than 0.5% of the dose after 48 hr. The concentrations of radioactivity in excised tissues were less than 0.04% of the administered dose.
Details on excretion:
The data demonstrated rapid absorption and elimination of orally administered CHDM, with renal excretion accounting for 89-96% of the dose within 48 hours of test substance administration. Radioactivity in the feces accounted for 1.2-3.0% of the administered dose while levels in expired CO2 accounted for only 0.01-0.05% of the total radioactivity. Less than 0.40% of the administered radioactivity was retained in the tissues, organs and carcass. Together with acetone and water soluble radioactivity collected as cage washings (1.02-6.61%), total radioactivity recovered averaged 98.9% of the dose.
Toxicokinetic parameters
Test no.:
#1
Toxicokinetic parameters:
half-life 1st: The half-life of CHDM in blood was 13.25 minutes; 100% of the [14]C CHDM added to whole blood was recovered in the plasma.

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
METABOLITES IN BLOOD:
Heparinized blood from rats dosed with unlabeled CHDM was separated by centrifugation, the plasma extracted with diethyl ether, and the extracts analyzed by gas chromatography (GC) and GC-MS. Plasma from rats dosed with 400 mg/kg bw CHDM resulted in 2 GC peaks with retention times and mass spectra corresponding to authentic samples of cis-cyclohexanedimethanol (cis-CHDM) and trans-cyclohexanedimethanol (trans-CHDM). Two additional compounds were characterized by GC-MS: cis-4-hydroxymethylcyclohexanecarboxylic acid and trans-4- hydroxymethylcyclohexanecarboxylic acid.

METABOLITES IN URINE:
When 24-hr urine samples from each rat dosed with [14]C CHDM were acidified and extracted with diethyl ether, less than 2% of the radioactivity remained in the aqueous phase. The ether soluble fractions were evaporated to dryness and derivatized with trimethylsilyl. Four GC peaks corresponding to the retention times and mass spectra of authentic samples of cis- and trans-4-hydroxymethylcyclohexanecarboxylic acid, and cis- and trans-cyclohexanedicarboxylic acid were detected for each rat at each dose level. The predominant metabolite for both sexes was cyclohexanedicarboxylic acid which accounted for about 68% of the dose. About 31% of the dose was excreted as 4-hydroxymethylcyclohexanecarboxylic acid.

The aqueous phase remaining after ether extraction was treated with beta-glucuronidase or 6N or 12N HCl and then extracted with ether. Beta-glucuronidase treatment had no effect on the extractability of the remaining radioactivity. Mild acid hydrolysis solubilized about 50% of the radioactivity while strong acid solubilized nearly 100%. These results suggest the presence of one or more glycine conjugates of the oxidation products of CHDM.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): low bioaccumulation potential based on study results
The results indicate that, at dose levels up to 400 mg/kg bw, orally administered 1,4-cyclohexanedimethanol is rapidly absorbed, metabolized and eliminated by male and female rats. Almost all of the orally administered [14]C CHDM was excreted in the urine (89-96%), with smaller amounts eliminated in feces (1.2-3.0%) and expired CO2 (0.01-0.05%). Less than 0.5% was retained in the tissues and carcass. Total recovery, 48 hr after dosing, was 97.9-99.7% of the administered radioactivity. Unchanged CHDM was identified in blood but not urine. Metabolites identified in urine and/or blood were cis- and trans-4-hydroxymethylcyclohexanecarboxylic acid, and cis- and trans-cyclohexanedicarboxylic acid.
Executive summary:

In a metabolic fate and disposition study, radiolabeled 1,4-cyclohexanedimethanol ([14]C CHDM) was administered to male and female CD-COBS rats by gavage at dose levels of 40 or 400 mg/kg bw. CHDM was rapidly absorbed and excreted, with renal excretion accounting for elimination of 89-96% of the dose within 48 hours of test article administration. Radioactivity in the feces accounted for 1.2-3.0% of the dose while expired CO2 accounted for 0.01-0.05%. Less than 0.50% of the administered radioactivity was retained in the tissues, organs and carcass. Together with acetone and water soluble radioactivity collected as cage washings, total radioactivity recovered accounted for 97.9-99.7% of the dose. Although total radioactivity recovered in 48-hr urines and cage washings suggested similar excretion rates for both sexes dosed with 400 mg/kg bw, females excreted a smaller amount of 4-hydroxymethylcyclohexanecarboxylic acid than males (24% vs. 31% of the urinary metabolites).  

The metabolic pathway for CHDM appears to consist of a series of oxidation reactions that ultimately yield cyclohexanedicarboxylic acid. It appears that the methanol groups of CHDM are oxidized to aldehyde groups which are further oxidized to carboxyl groups. A partial oxidation product, 4-hydroxymethylcyclohexanecarboxylic acid, was identified in blood and urine and the terminal oxidation product, cyclohexanedicarboxylic acid, was identified in the urine. Urinary ether extraction studies suggest a small amount of radioactivity may be attributed to a glycine conjugate of one or more of the oxidation products of CHDM. The cis-trans ratio of metabolites excreted in the urine by rats was the same as the ratio of the original dose (about 70% trans- and 30% cis-).