Fig. 4.

Embryonic exposure to dioxin leads to DV closure in Ahr^fxneo and Arnt^fxneo hypomorphs. Timed matings of heterozygous (Ahr^fxneo/+) AHR hypomorph females and homozygous (Ahr^fxneo/fxneo) AHR hypomorph males were performed. At various stages of gestation, pregnant females were given an i.p. injection of 25 μg/kg dioxin or vehicle (DMSO) alone. The DV status of the resulting progeny was assessed by radiography or Trypan blue liver perfusion when the pups were 4–6 weeks old. Similar studies were performed with the ARNT hypomorphs and Ahr-null mice, and injections of pregnant females were performed at E16.5 and E18.5, respectively. Approximately half of the Ahr-null mice in the vehicle group received DMSO at E18.5, while the other half received no treatment during development. (A) Liver vascular architecture of an untreated Ahr^fxneo/fxneo hypomorph (Left) and an Ahr^fxneo/fxneo hypomorph after in utero exposure to dioxin at E14.5 (Right). (B) Frequency of DV closure in adult AHR Ahr^fxneo hypomorphs, Arnt^fxneo hypomorphs, and Ahr-null mice after in utero exposure to either dioxin or vehicle (DMSO) at various stages of gestation.