Gonadal differentiation in frogs exposed to estrogenic and antiestrogenic compounds

Abstract

Exposure of amphibians to endocrine disrupting compounds (EDCs) may alter differentiation of gonads, especially when exposures begin during early life stages. Gonadal differentiation was observed in leopard frogs (Rana pipiens) and wood frogs (Rana sylvatica) exposed as tadpoles to estrogenic (estradiol, ethinylestradiol, nonylphenol) and antiestrogenic compounds (an aromatase inhibitor, flavone, and an antiestrogen, ICI 182780). Exposure to all compounds at micrograms/L concentrations altered gonadal differentiation in some animals by inducing either complete feminization or an intersex condition, and altered testicular tubule morphology, increased germ cell maturation (vitellogenesis), and oocyte atresia. Comparisons between the two species indicate that R. pipiens are more susceptible to sex reversal and development of intersex gonads. However, R. sylvatica also showed alterations to testicular morphology, germ cell maturation, and ooctye atresia. These laboratory results indicate that amphibians could be susceptible to altered gonadal differentiation and development when exposed to estrogenic and antiestrogenic compounds in aquatic environments, such as those impacted by agricultural, industrial, and municipal runoff.

Determining the optimal developmental stages of Xenopus laevis for initiating exposures to chemicals for sensitively detecting their feminizing effects on gonadal differentiation

“…We observed that EE2 did not significantly affect the survival of the X. laevis tadpoles, which were the same with other amphibians, such as M. ornate, L. pipiens (MacKenzie et al, 2003;Mali and Gramapurohit, 2016). In present study, 1 nM EE2 prolonged the time to reach stage 58 of X. laevis (Table 3).…”

Derivation of an Aquatic Predicted No-Effect Concentration for the Synthetic Hormone, 17α-Ethinyl Estradiol

“…f For C. riparius, a worst-case NOEC of 100 ng EE2/L is used, based on the unbounded LOEC of >100 ng EE2/L. g For amphibians, the relatively high unbounded values of <1000 ng EE2/L for the frogs R. pipiens and R. sylvatica (62) and <784 ng EE2/L for the frog X. (Silurana) tropicalis (61) were discarded from the data set.…”

The pathway to femaleness: current knowledge on embryonic development of the ovary

“…In these species, estrogen is the ovary-determining factor. Estrogen treatment of male embryos during the critical period of development in fish (Guiguen et al, 1999;Kobayashi et al, 2003), frogs (Mackenzie et al, 2003;Kato et al, 2004), reptiles (Pieau and Dorizzi, 2004), chicks (Abinawanto et al, 1996;Mittwoch, 1998;Akazome and Mori, 1999), or in marsupial newborns (Shaw et al, 1988;Baker et al, 1993;Fadem, 2000;Coveney et al, 2001;Renfree et al, 2001) can cause testis-to-ovary sex reversal. In addition, inhibition of estrogen synthesis in female embryos leads to testis development in these species.…”