摘要：Cadmium (Cd), one of the most common endocrine disruptors (EDCs), plays an important role in sexdifferentiation by blocking receptors of sex steroid hormones in amphibians. To analyse the influence of Cdon gonadal sex differentiation of spot frog (Pelophylax nigromaculata) larvae, the fertilized eggs were exposedto Cd (100, 10, 1 and 0.1 µg/L) in water until complete metamorphosis. We observed sex ratio and gonadalcondition, detected the expression and location of estrogen receptor (ER) and metallothioneins (MTs) on thegonad cells by immunohistochemical method. Some intersex gonads (the same gonad has testicular andovarian-like elements) in Cd treatment at 10, 1 and 0.1 µg/L were observed. Compared to control, female/male ratios at Cd treatment levels (1 and 0.1 µg/L) were significantly different (p< 0.05). ER and MTs werepositively expressed in the cytoplasm and nuclei of gonad, and the expression of ER and MTs did not showa monotonic linear relationship in the Cd treatment. In the relatively lower concentration (10, 1 and 0.1 µg/L),ER and MTs expressions were stronger, while it appeared to be weak immunoreactivity in higher concentration(100 µg/L). The expression and location of ER and MTs on the gonad cells and sex ratios were affected byCd, indicating that Cd has estrogenic effect on P. nigromaculata.
