Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on molar development among non-resistant inbred strains of mice: a geometric morphometric analysis.

Prenatal development is highly sensitive to the effects of environmental contaminants. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an environmental toxicant that at very low levels causes teratogenic effects such as irregular tooth development. Variations in susceptibility to TCDD's effects have been attributed primarily to differences at the Ahr locus. There is some evidence, however, that genes at other loci may be involved in mediating TCDD's effects on various endpoints. Our hypothesis therefore was that the effect of TCDD on molar development would differ even among inbred mouse strains possessing similar Ahr alleles. To test this, geometric morphometric techniques were used to evaluate the effects of several different levels of TCDD on molar size, shape and asymmetry in the offspring of dosed females from five different inbred strains of mice bearing TCDD-sensitive Ahr alleles. The results indicated that a maternal dose of 1 microg TCDD/kg body weight on gestation day 13 altered the shape (but not the size or asymmetry) of the first two molars in mice from the C3H/HeJ and CBA/J strains of mice, but not in mice from the other strains. The C3H/HeJ and CBA/J strains appeared to be the most sensitive to the disruption of molar development via TCDD and the C57BL/6J strain appeared to be the least sensitive.