Registration Dossier

Administrative data

Endpoint:
mechanistic studies
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
no data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was performed by the NTP in support of an earlier 90 day study to further investigate the mechanism of action of cardiotoxicity. No specific guideline was followed. There is no data on GLP. The publication describeds the findings in detail.

Data source

Reference
Reference Type:
publication
Title:
Critical Pathways in Heart Function: Bis(2-chloroethoxy)methane-Induced Heart Gene Transcript Change in F344 Rats
Author:
Dunnick, J., Blackshear, P., Kissling, G., Cunningham, M., Parker, J., Nyska, A.
Year:
2006
Bibliographic source:
Toxicologic Pathology, 34:348–356, 2006

Materials and methods

Test guideline
Qualifier:
no guideline followed
GLP compliance:
not specified
Type of method:
in vivo
Endpoint addressed:
not applicable

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Chemical name: Bis(2-chloroethoxy)methane
Batch No.: lot B007269977
Supplier: Karl Industries, Aurora, Ohio,
Purity: 98.5% pure (National Toxicology Program, 2000).

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male

Administration / exposure

Route of administration:
dermal
Vehicle:
ethanol
Analytical verification of doses or concentrations:
yes
Duration of treatment / exposure:
16 days
Frequency of treatment:
Solutions of CEM were prepared in 95% ethanol for dosing by dermal administration daily, excluding weekends, for two weeks plus two consecutive dosages before the last sacrifice on study-day 16, at which animals had received a total of 12 doses.
Post exposure period:
None
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 200, 400, 600 mg/kg bw
Basis:
nominal conc.
No. of animals per sex per dose:
12 (RNA was extracted from hearts of 6 control rats, and from 6 rats from each treatment group (200, 400, or 600 mg/kg) at day 2 and day 5 just 1 hour after dosing.)
Control animals:
yes, concurrent vehicle

Results and discussion

Details on results:
The down-regulation of ATP subunit transcripts (Atp5j, ATP5k), which reside in the mitochondrial membranes, indicated a decrease in energy supply at day 2 and day 5. This was accompanied by down-regulation of transcripts involved in high-energy consumption processes such as membrane transport and ion channel transcripts (e.g., abc1a, kcnj12). The up-regulation of transcripts encoding for temperature regulation and calcium binding proteins (ucp1 and calb3) only at the 2 low exposure levels, suggest that these adaptive processes cannot occur in association with severe cardiotoxicity as seen in hearts at the high exposure level. Transcript expression changes occurred within 2 days of CEM exposure, and were dose- and time-dependent.

Applicant's summary and conclusion

Conclusions:
Gene transcript changes after exposure to the heart toxin, bis(2-chloroethoxy)methane (CEM), were analyzed to elucidate mechanisms in cardiotoxicity and recovery. The heart transcript changes suggest that CEM cardiotoxicity activates protective processes associated energy conservation and maintenance of heart function.
Executive summary:

Gene transcript changes after exposure to the heart toxin, bis(2-chloroethoxy)methane (CEM), were analyzed to elucidate mechanisms in cardiotoxicity

and recovery. CEM was administered to 5-week-old male F344/N rats at 0, 200, 400, or 600 mg/kg by dermal exposure, 5 days per week, for a total of 12 doses by study day 16. Heart toxicity occurred after 2 days of dosing in all 3 regions of the heart (atrium, ventricle, interventricular septum) and was characterized by myofiber vacuolation, necrosis, mononuclear-cell infiltration, and atrial thrombosis. Ultrastructural analysis revealed that the primary site of damage was the mitochondrion. By day 5, even though dosing was continued, the toxic lesions in the heart began to resolve, and by study day 16, the heart appeared histologically normal. RNA was extracted from whole hearts after 2 or 5 days of CEM dosing. After a screen for transcript change by microarray analysis, dose-response trends for selected transcripts were analyzed by qRT-PCR. The selected transcripts code for proteins involved in energy production, control of calcium levels, and maintenance of heart function. The down-regulation of ATP subunit transcripts (Atp5j, ATP5k), which reside in the mitochondrial membranes, indicated a decrease in energy supply at day 2 and day 5. This was accompanied by down-regulation of transcripts involved in high-energy consumption processes such as membrane transport and ion channel transcripts (e.g., abc1a, kcnj12). The up-regulation of transcripts encoding for temperature regulation and calcium binding proteins (ucp1 and calb3) only at the 2 low exposure levels, suggest that these adaptive processes cannot occur in association with severe cardiotoxicity as seen in hearts at the high exposure level. Transcript expression changes occurred within 2 days of CEM exposure, and were dose- and time-dependent. The heart transcript changes suggest that CEM cardiotoxicity activates protective processes associated energy conservation and maintenance of heart function.