Hatcol 1760

Endpoint summary

Description of key information

The submission substance was found to be non-toxic during a 28-day repeat dose oral exposure study in the rat.
Repeat dose studies via the dermal and inhalation routes of exposure were not conducted on the basis of a lack of exposure to the submission substance.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEL

250 mg/kg bw/day

Additional information

The study was designed to investigate the systemic toxicity and potential adverse effects of the test material on reproduction (including offspring development) and complies with the recommendations of the OECD Guidelines for Testing of Chemicals No. 422 “Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test” (adopted 22 March 1996).

The test material was administered by gavage to three groups each of ten male and ten femaleWistar Han™:HsdRccHan™:WIST strain rats, for up to fifty-four consecutive days (including a two week maturation phase, pairing, gestation and early lactation for females), at dose levels of 50, 250 and 1000 mg/kg/day. A control group of ten males and ten females was dosed with vehicle alone (Arachis Oil BP). Two recovery groups, each of five males and five females, were treated with the high dose (1000 mg/kg/day) or the vehicle alone for forty-two consecutive days and then maintained without treatment for a further fourteen days.

Clinical signs, behavioural assessments, bodyweight development, food and water consumption were monitored during the study. Haematology and blood chemistry were evaluated prior to mating and at termination on five selected non-recovery males and females from each dose group. In addition, haematology and blood chemistry were evaluated after the fourteen day treatment free period on all recovery animals. Urinalysis was evaluated on five selected non-recovery males at the end of the treatment period and for all recovery group males at the end of the treatment free period.

Pairing of animals within each non-recovery dose group was undertaken on a one male: one female basis within each treatment group on Day 15 of the study, with females subsequently being allowed to litter and rear their offspring to Day 5post partum.

During the lactation phase, daily clinical observations were performed on all surviving offspring, together with litter size and offspring weights and assessment of surface righting reflex.

Extensive functional observations were performed on five selected males from each non-recovery dose group after the completion of the mating phase, and for five selected parental females from each non-recovery dose group on Day 4post partum.

Surviving non-recovery males were terminated on Day 43, followed by the termination of all non-recovery females and offspring on Day 5post partum. All non-recovery animals were subjected to a gross necropsy examination and histopathological evaluation of selected tissues was performed.

Recovery animals were treated according to the dose group continuously up to the point of sacrifice of the non-recovery males at which time the treatment was discontinued. After fourteen days without treatment, the recovery males and females were subjected to a gross necropsy examination and histopathological evaluation of selected tissues was performed.

Results

Adult Responses:

Mortality.There were no treatment-related unscheduled deaths during the study.

Clinical Signs.No toxicologically significant clinical signs were evident in terminal kill animals throughout the study.

Behavioural Assessment.There were no treatment-related changes in the behavioural parameters measured.

Functional Performance Tests.There were no toxicologically significant changes in the functional performance parameters measured.

Sensory Reactivity Assessments.There were no treatment-related changes in sensory reactivity.

Bodyweights.No adverse effect on bodyweight development was detected.

Food Consumption and Food Efficiency.No adverse effect on dietary intake or food efficiency was detected.

Water Consumptions.No intergroup differences were detected.

Haematology.No toxicologically significant effects were detected in the haematological parameters measured.

Blood Chemistry.Non-recovery females treated with 1000 mg/kg/day showed an increase in cholesterol. No such effects were evident for non-recovery males treated with 1000 mg/kg/day, animals of either sex treated with 250 or 50 mg/kg/day or recovery animals following fourteen days without treatment.

Urinalysis.No treatment-related effect was detected in the urinalytical parameters measured.

Pathology.

Necropsy. No toxicologically significant macroscopic abnormalities were detected for adults or offspring.

Organ Weights.Non-recovery animals of either sex treated with 1000 mg/kg/day showed an increase relative liver weight. Absolute liver weight was also elevated in non-recovery 1000 mg/kg/day females. No such effects were detected in animals of either sex treated with 250 or 50 mg/kg/day.

Histopathology.The following treatment-related changes were detected:

ADRENAL GLAND:Hypertrophy of the zona glomerulosa was seen in relation to treatment for males only at all treatment levels. This change is regarded as adaptive in nature and may be associated with renal changes.

The condition was observed to have regressed among Recovery 1000 mg/kg/day animals following an additional 14 days without treatment.

LIVER:Centrilobular hepatocyte enlargement was seen as a consequence of treatment for males treated with 1000 mg/kg/day but not at any other treatment level. There was no evidence of a similar effect for females.

The condition was observed to have regressed following completion of the recovery period.

Hepatocyte enlargement is commonly observed in the rodent liver following the administration of xenobiotics and, in the absence of associated inflammatory or degenerative changes, is generally considered to be adaptive in nature.

KIDNEYS:Renal changes characterised by globular accumulations of eosinophilic material, tubular basophilia/degeneration, and tubular necrosis, were seen among males only treated with 1000 mg/kg/day. Globular accumulations of eosinophilic material were also seen for males treated with 250 mg/kg/day or at 50 mg/kg/day with tubular necrosis in a few males treated with 250 mg/kg/day. Similar accumulations were also demonstrated by examination of Mallory’s Heidenhain stained sections of kidney which assists in the diagnosis of but which is not diagnostic forα₂-Microglobulin.

There was regression of globular accumulations of eosinophilic material among Recovery 1000 mg/kg/day males following completion of the 14-day recovery period although residual tubular necrosis remained in four animals, possibly with an associated higher incidence/severity of isolated groups of basophilic tubules. 

The presence of globular accumulations of eosinophilic material is consistentwith hydrocarbon nephropathy, which results from the excessive accumulation ofα₂-microglobulinin renal proximal tubular epithelial cells. α₂-Microglobulin is found only in the proximal tubular epithelium of adult males.

THYROID:Follicular cell hypertrophy was seen in relation to treatment for males treated with 1000 mg/kg/day, but not convincingly at any other treatment level. Females were not similarly affected. There was no difference in incidence or severity of the condition between Recovery 1000 mg/kg/day and Recovery control animals following completion of the recovery period.

THYMUS:Lymphoid atrophy was observed as a consequence of treatment for females treated with 1000 mg/kg/day but not at any other treatment level. Males were not similarly affected.

The condition was observed to have regressed among recovery group animals following completion of an additional fourteen days without treatment.

Conclusion.The oral administration of Hatcol 1760 to rats by gavage, at dose levels of 50, 250 and 1000 mg/kg/day, resulted in treatment-related effect in males from all treatment groups and in females treated with 1000 mg/kg/day. A No Observed Effect Level (NOEL) has, therefore not been established for males however, no such changes were demonstrated at 250 mg/kg/day for females and the ‘No Observed Effect Level’ (NOEL) for females was, therefore considered to be 250 mg/kg/day.

The kidney changes identified histopathologically at 250 and 50 mg/kg/day were consistent with well documented changes that are peculiar to the male rat in response to treatment with some hydrocarbons. There is no evidence to suggest that the tubular necrosis seen in a few 250 mg/kg/day males is of independent origin since it is only seen in association with hydrocarbon nephropathy and was not observed among female rats. It is therefore considered to be associated with, or a consequence of, excessive accumulation of alpha-2-microglobulin in male rats in this investigation. This effect is, therefore, not indicative of a hazard to human health and, for the purposes of hazard evaluation, the “No Observed Adverse Effect Level” (NOAEL) for males, should be regarded as 250 mg/kg/day.

Offspring from litters treated with 1000 mg/kg/day showed a reduction in bodyweight gain between days 1 and 4post partum. The ‘No Observed Effect Level’ (NOEL) for reproductive toxicity was therefore considered to be 250 mg/kg/day.

The effects seen at 1000 mg/kg/day are minimal and because of higher litter size and the fact that there is offspring bodyweight gain albeit at a lower rate than controls, the NOAEL can be suggested as 1000 mg/kg/day.

This study was ranked as Relaibility 1 according to the Klimisch et al scale, as it was conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of relevant results.

A repeat dose dermal toxicity study was not conducted on the submisson substance as dermal contact during formulation and use is unlikely, and physicochemical and toxicological properties do not suggest a significant rate of absorption through the skin.

Testing by the inhalation route of exposure is considered inappropriate as exposure to humans via inhalation is considered unlikely, as there is no possibility of exposure to aerosols, particles or droplets of an inhalable size.

Justification for classification or non-classification

The submission substance did not meet the criteria for classification as toxic or harmful by the oral route of exposure during a 28 -day repeat dose toxicity study in the rat.