Effects of paraquat and glyphosate on steroidogenesis in gonads of the frog Rana esculenta in vitro

Herbicides are toxic for amphibians, influencing various developmental stages. In particular, paraquat and glyphosate have teratogenic effects on tadpole development, though little information is available on how they affect reproduction in amphibians. In the present work, ovarian tissue and testis of the water frog Rana esculenta were incubated in vitro in presence of different concentrations of the two herbicides. 17β-estradiol and testosterone levels were measured in the incubation medium by radioimmunoassay. The data showed that paraquat inhibited testosterone and 17β-estradiol production, with the lowest-observed-effect concentration (LOEC) of 10⁻⁴ M, while paraquat inhibition of steroidogenesis in amphibian gonads was reversed by the presence of epigallocatechin gallate in the culture medium. These result indicates that paraquat acts on gonadal steridogenesis through a mechanism involving reactive oxygen species. Glyphosate showed no effect on gonadal steroidogenesis. These results suggest that paraquat may interfere in amphibian reproductive processes.