Tebuconazole disrupts steroidogenesis in Xenopus laevis

Area of Science:

• Endocrinology
• Environmental Toxicology
• Aquatic Biology

Background:

• Steroidogenesis is crucial for reproductive health.
• Fungicides like tebuconazole can act as endocrine disruptors.
• African clawed frogs (Xenopus laevis) are sensitive models for environmental contaminants.

Purpose of the Study:

• To investigate the mechanism of tebuconazole-induced disruption of steroidogenesis in Xenopus laevis.
• To determine dose-dependent and time-dependent effects of tebuconazole on hormone levels.
• To explore the impact of tebuconazole on specific steroidogenic enzymes.

Main Methods:

• Controlled 27-day exposure of Xenopus laevis to tebuconazole.
• Quantification of tebuconazole in tissues using LC-MS/MS.
• Measurement of steroid hormones (testosterone, dihydrotestosterone, 17β-estradiol) in plasma and gonads using LC-MS/MS and GC-MS/MS.
• Assessment of androgen levels via radioimmunoassay.
• Analysis of CYP17 enzyme expression.

Main Results:

• Tebuconazole bioconcentrated in frog tissues (BCF up to 238).
• Low-dose tebuconazole (0.1μgL⁻¹) decreased plasma testosterone and dihydrotestosterone.
• High-dose tebuconazole (100 and 500μgL⁻¹) increased plasma testosterone and dihydrotestosterone initially, but decreased 17β-estradiol.
• Prolonged high-dose exposure persisted in suppressing 17β-estradiol and increased gonadal testosterone, dihydrotestosterone, and CYP17 expression.

Conclusions:

• Tebuconazole exhibits complex, dose-dependent effects on frog steroidogenesis.
• Low doses may inhibit CYP17, while high doses appear to suppress CYP19, leading to altered androgen and estrogen levels.
• Observed increases in gonadal androgens may indicate compensatory mechanisms in response to endocrine disruption.