Figure 4.

Staining for proliferation, target-gene induction, and AhR expression in glandular stomachs from control or TCDD-treated wild-type mice and CA-AhR mice. Nine-month-old wild-type (wt) or CA-AhR males were treated orally with vehicle (oil) or 10 μg of TCDD/kg of body weight, and tissues were removed and fixed in formaldehyde 4 days later. Paraffin-embedded serial sections were stained with HE (A–C) or immunostained with antibodies specific for PCNA (D–F), CYP1A1 (G–I), or AhR (J–O). Incubation without primary antibody was used as negative control. (Bars in A–L, 0.25 mm; bars in M–O, 0.015 mm.) The brackets, arrows, and star indicate reference points in the serial sections. (D–F) The proliferative zone shown by PCNA staining (brackets) is expanded basally into the parietal/chief cell region in stomachs from TCDD-treated wild-type animals and CA-AhR animals. The arrow indicates proliferation in submucosal tumors in the CA-AhR stomach. (G–I) Examples of CYP1A1 staining are shown by arrows. The star indicates strong CYP1A1 expression in the submucosal tumor. (J–O) AhR is expressed throughout the glandular stomach of both wild-type and CA-AhR mice. The arrow in L indicates a submucosal tumor. The arrow in O indicates mainly nuclear staining in the stomach of CA-AhR mice.