Effects of dibutyl phthalate as an environmental endocrine disruptor on gonadal sex differentiation of genetic males of the frog Rana rugosa.

Abstract

To examine the effects of dibutyl phthalate (DBP) on gonadal sex differentiation, genetically male tadpoles of Rana rugosa were exposed to dilute solutions of DBP at concentrations of 0.1, 1, or 10 microM during days 19-23 after fertilization, which is the critical period of gonadal sex differentiation in R. rugosa. Tadpoles were necropsied on day 40. The genetically male tadpoles were produced from crossings between males (ZZ) of one local population, in which females are the heterogametic sex, and females (XX) of another local population, in which males are the heterogametic sex. As positive control groups, tadpoles were exposed to dilute solutions of 17beta-estradiol (E(2)) at concentrations of 0. 01, 0.1, or 1 microM during the same period. The internal structure of the gonads was histologically examined in a total of 30 control tadpoles, 86 E(2)-treated tadpoles, and 90 DBP-treated tadpoles. The gonads of the control tadpoles all showed the typical structure of testes. In contrast, 0.01, 0.1, and 1 microM E(2) treatments caused the undifferentiated gonads of 18, 63, and 100% of the tadpoles, respectively, to develop into gonads of complete or partial ovarian structure. After 0.1, 1, and 10 microM DBP treatment, 0, 7, and 17% of tadpoles, respectively, were similarly affected. These findings suggest that DBP was about 1,000-fold less potent than E(2). Nevertheless, DBP is an environmentally dangerous hormone that disrupts the pathways of testicular differentiation in genetically male animals.

Impact of butyl benzyl phthalate on development of the reproductive system of European pikeperch, Sander lucioperca (L.)

“…Another ester, di-n-butyl phthalate (DBP), induced the occurrence of intersex specimens and sex inversion in studies conducted on genetic males of the Japanese wrinkled frog (Rana rugosa) (Ohtani et al, 2000). Also, following exposure to DBP, the African clawed frog (Xenopus laevis), exhibited delayed spermatogenesis and symptoms of feminisation manifesting as well-developed fallopian tubes in the testes (Lee and Veeramachaneni, 2005).…”

Effects of Chinese domestic polychlorinated biphenyls (PCBs) on gonadal differentiation in Xenopus laevis.

“…Environmental Health Perspectives • VOLUME 111 | NUMBER 4 | April 2003 intersexuality induced by PCB 3 and PCB 5 in X. laevis as well as previous studies suggest that endocrine disruptors can affect gonadal differentiation in amphibians and that this kind of chemical may be a factor leading to population declines (Hayes et al 2002;Kloas et al 1999;Ohtani et al 2000Ohtani et al , 2001. Therefore, it is necessary to develop a model using a representative species to study the effects of endocrine disruptors on amphibians.…”

“…Certainly, other amphibian species might have also their own advantages. For example, genetic males in Rana rugosa can be induced (Ohtani et al 2000), and feminization in Hyperolius argus can be identified directly by sex coloration (Noriega and Hayes 2000). However, the most serious disadvantage of these species is that they have not been used broadly as typical experimental animals.…”

“…Kloas et al (1999) reported that bisphenol A and 4-nonylphenol significantly altered the sex ratio in Xenopus laevis. Dibutyl phthalate and styrene induced gonadal feminization in Rana rugosa (Ohtani et al 2000(Ohtani et al , 2001. Recently, hermaphroditic gonads induced by atrazine in X. laevis were reported by Hayes et al (2002).…”

Potential ecotoxic effects of polychlorinated biphenyls on Xenopus laevis

“…Amphibians are susceptible to environmental contaminants because of their permeable skins and a biphasic life cycle [11,12]. Increasing evidence suggests that gonadal development of amphibians is especially sensitive to endocrine disruptors [13][14][15]. Although high accumulation of PCBs in wild amphibians highlights the need to examine the potential role of PCBs in the amphibian population, the available information regarding toxic effects of PCBs on amphibians has been very limited so far [16,17].…”