No effects of the antiandrogens cyproterone acetate (CPA), flutamide and p,p'-DDE on early sexual differentiation but CPA-induced retardation of embryonic development in the domestic fowl (Gallus gallus domesticus)

Because a wide range of environmental contaminants are known to cause endocrine disorders in humans and animals, in vivo tests are needed to identify such endocrine disrupting chemicals (EDCs) and to assess their biological effects. Despite the lack of a standardized guideline, the avian embryo has been shown to be a promising model system which responds sensitively to EDCs. After previous studies on the effects of estrogenic, antiestrogenic and androgenic substances, the present work focuses on the effects of in ovo exposure to p,p'-DDE, flutamide and cyproterone acetate (CPA) as antiandrogenic model compounds regarding gonadal sex differentiation and embryonic development of the domestic fowl (Gallus gallus domesticus). The substances were injected into the yolk of fertilized eggs on embryonic day one. On embryonic day 19 sex genotype and phenotype were determined, followed by gross morphological and histological examination of the gonads. Treatment with flutamide (0.5, 5, 50 µg/g egg), p,p'-DDE (0.5, 5, 50 µg/g egg) or CPA (0.2, 2, 20 µg/g egg) did not affect male or female gonad development, assessed by gonad surface area and cortex thickness in both sexes and by the percentage of seminiferous tubules in males as endpoints. This leads to the conclusion that antiandrogens do not affect sexual differentiation during embryonic development of G. gallus domesticus, reflecting that gonads are not target organs for androgens in birds. In ovo exposure to 2 and 20 µg CPA/g egg, however, resulted in significantly smaller embryos as displayed by shortened lengths of skull, ulna and tarsometatarsus. Although gonadal endpoints were not affected by antiandrogens, the embryo of G. gallus domesticus is shown to be a suitable test system for the identification of substance-related mortality and developmental delays.

Morphological and transcriptomic effects of endocrine modulators on the gonadal differentiation of chicken embryos: The case of tributyltin (TBT)

Morphological malformations induced by tributyltin (TBT) exposure during embryonic development have already been characterized in various taxonomic groups, but, nonetheless, the molecular processes underlying these changes remain obscure. The present study provides the first genome-wide screening for differentially expressed genes that are linked to morphological alterations of gonadal tissue from chicken embryos after exposure to TBT. We applied a single injection of TBT (between 0.5 and 30 pg as Sn/g egg) into incubated fertile eggs to simulate maternal transfer of the endocrine disruptive compound. Methyltestosterone (MT) served as a positive control (30 pg/g egg). After 19 days of incubation, structural features of the gonads as well as genome-wide gene expression profiles were assessed simultaneously. TBT induced significant morphological and histological malformations of gonadal tissue from female embryos that show a virilization of the ovaries. This phenotypical virilization was mirrored by altered expression profiles of sex-dependent genes. Among these are several transcription and growth factors (e.g. FGF12, CTCF, NFIB), whose altered expression might serve as a set of markers for early identification of endocrine active chemicals that affect embryonic development by transcriptome profiling without the need of elaborate histological analyses.

Applicability of lectin histochemistry in a test system with in ovo treatment for detecting androgenic and antiandrogenic effects of chemicals in Japanese quail (Coturnix japonica)

The aim of the current study was to examine whether analysis of the appearance of specific lectin-positive substances in the quail embryonic cloacal gland would be useful for evaluating the androgenic and antiandrogenic effects of chemicals. Fertilized Japanese quail eggs were injected with 0 to 75 µg of cyproterone acetate (CA), an antiandrogenic compound, on d 12 of incubation (d 12), followed by injection of 0 to 300 µg of testosterone propionate (TP) on d 13. Experimental groups consisted of a control group (corn oil injections on d 12 and 13), a TP-L group [corn oil and a low dose (L; 30 µg) of TP], a TP-H group [corn oil and a high dose (H; 300 µg) of TP], a CA-L + TP-H group [a low dose (L;7.5 µg) of CA + TP-H], and a CA-H + TP-H group [a high dose (H; 75 µg) of CA + TP-H]. The cloacal tissues were collected on d 16, processed into paraffin sections, and stained using 14 different biotinylated lectins. The Vicia villosa (VVA) lectin most strongly stained the developing cloacal glandular cells in TP-H. Western blotting analysis showed 1 VVA-positive band of approximately 75 kDa. The ratio of VVA-positive areas per unit square examined microscopically by image analysis was significantly greater in the TP-H group than in the control group in both males and females. The ratio was significantly decreased in the CA-L + TP-H and CA-H + TP-H groups compared with the TP-H group in both males and females. Furthermore, the ratio was smaller in females than in males within a TP-L or TP-H treatment group. These results suggest that lectin histochemistry on quail embryonic cloaca using VVA is useful for evaluating the androgenic and antiandrogenic effects of chemical compounds.