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Zhan-Fen Qin, Jing-Ming Zhou, Shao-Gang Chu, and Xiao-Bai Xu

Research Center for Eco-environmental Sciences, the Chinese Academy of Sciences, Beijing, China

Abstract

To determine whether polychlorinated biphenyls (PCBs) influence gonadal differentiation in Xenopus laevis, tadpoles were exposed to two Chinese domestic PCBs (PCB₃ and PCB₅) from Nieuwkoop and Faber stage 46/47 to complete metamorphosis. Gonads were characterized using a dissecting microscope. The control X. laevis had normal ovaries or testes in gross morphology, whereas obviously abnormal testes including ovotestes were found in PCB₃- and PCB₅-exposed groups. Ovotestes were characterized by morphologic ovaries in the cranial and caudal parts and morphologic testes in the middle part. PCBs did not alter the percentage of females but reduced the percentage of males with morphologically normal testes. The histologic structure of gonads was examined by a series of sections. Morphologically normal and abnormal testes from a few frogs exposed to PCBs were interspersed with oocytes in histologic sections. These testes exhibited looser structure with fewer seminiferous tubes, spermatogonia, and spermatozoa than in controls. The findings suggest that PCB₃ and PCB₅ have significant feminization effects on gonadal differentiation in X. laevis and that this species is sensitive to endocrine disruption and may be used as a good model to study endocrine disruption. Key words: endocrine disruptor, gonadal differentiation, ovotestis, PCB₃, PCB₅, polychlorinated biphenyls, Xenopus laevis. Environ Health Perspect 111:553-556 (2003) .