Effects of steroids and dioxin (2,3,7,8-TCDD) on the developing wolffian ducts of the tiger salamander ( Ambystoma tigrinum)

Abstract

This study was undertaken to investigate effects of the prototypical dioxin, 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) on steroid-dependent development of the wolffian ducts of an amphibian, the tiger salamander ( Ambystoma tigrinum). Larvae with immature gonads and undeveloped müllerian ducts were injected with the steroid hormones estradiol (E 2), dihydrotestosterone (DHT), or vehicle alone. Additionally, steroid-treated and vehicle-control larvae were immersed in sub-lethal solutions of technical grade TCDD (0, 0.0003, 0.003, 0.03, 0.3, and 3.0 μg TCDD/L). Both steroid treatments stimulated hypertrophy of the wolffian duct epithelium and an increase in mean epithelial cell size. Only DHT treatment stimulated epithelial cell proliferation. TCDD stimulated wolffian duct hypertrophy through an increase in mean epithelial cell size. TCDD acted as an androgen agonist on wolffian duct epithelial area and epithelial cell size. TCDD had no effect on wolffian duct epithelium among E 2-injected animals. Stimulatory effects on cell size were observed at 0.0003 μg/L TCDD in saline-injected animals and at 0.003 μg/L TCDD in DHT-injected animals. Both E 2 and DHT stimulated growth of the wolffian ducts early in development. Technical grade TCDD alone mimics E 2 and DHT action but exhibits an androgen-agonistic action in the presence of exogenously administered DHT. Implications of possible interactions between TCDD and xenosteroids are discussed.