Effects of gestational exposure to ethane dimethanesulfonate in CD-1 mice: microtia and preliminary hearing tests.
BACKGROUND
Microtia is a reduction in pinna size, usually seen in humans in conjunction with other medical conditions. We report microtia in CD-1 mice after gestational exposure to ethane dimethanesulfonate (EDS), an alkylating agent and adult rat Leydig cell toxicant.


METHODS
Time-pregnant CD-1 mice were administered 0, 80, or 160 mg EDS/kg on gestation days (GD) 11-17, or 0 or 160 mg EDS/kg on GD 11-13, GD 13-15 or GD 15-17. Pinnae were measured on postnatal days (PND) 4, 8, 18, and 28; and were observed for detachment from birth through PND 8. Branchial-arch derived skeletal structures and histology of the pinna was examined on PND 4 and 24. Brainstem auditory evoked response (BAER) tests were carried out at approximately PND 160 to determine possible effects on hearing.


RESULTS
All offspring of EDS-treated dams exhibited bilateral, dose-related decreases in pinna size. Gestational exposure during GD 11-13 produced smaller ears than during GD 13-15 or 15-17, but not as small as the GD 11-17 regimen. Ossification of other pharyngeal arch derivatives was delayed whereas histology was unremarkable. BAER analysis showed a decrease in the proportion of adult offspring producing a quantifiable response to varied auditory stimuli among EDS-treated litters.


CONCLUSIONS
Gestational exposure to EDS affects pinna development in the mouse, with a broad period of sensitivity during the second half of gestation. Microtia induced by EDS may be associated with hearing deficits, suggesting functional importance of pinna size or additional effects of EDS on ear development not detected by morphological examination.
Tarka-Leeds
Dana K
DK
Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Herr
David W
DW
Klinefelter
Gary R
GR
Rogers
John M
JM
D000014:Abnormalities, Drug-Induced; D000818:Animals; D004425:Ear Cartilage / Q000002:abnormalities*; D004431:Ear, External / Q000002:abnormalities*; D005260:Female; D005865:Gestational Age; D034381:Hearing Loss / Q000139:chemically induced*; D006320:Hearing Tests; D008297:Male; D008698:Mesylates / Q000008:administration & dosage / Q000633:toxicity*; D009929:Organ Size / Q000187:drug effects; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats
D008698:Mesylates; C002994:ethylene dimethanesulfonate