“…There has been frequent use of the rat Gray et al, 1997;Huuskonen et al, 1994;Ikeda et al, 2005;Mably et al, 1992a,b,c) and mouse (Birnbaum et al, 1991;Ko et al, 2002;Neubert et al, 1973;Thackaberry et al, 2005;Weber and Birnbaum, 1985;Willey et al, 1998) as model systems to study the developmental toxicity of TCDD. However, only a few studies have utilized the hamster Olson and McGarrigle, 1992;Olson et al, 1990;Wolf et al, 1999) or guinea pig (Olson and McGarrigle, 1992). Our use of the guinea pig, rat and hamster (mature animal LD 50 values of 0.6-2, 22-60 and 1157-5051 g/kg, respectively) in this current study has allowed us to evaluate species that display a relatively low, medium and high sensitivity to TCDD.…”