Endosulfan alters fish gonadal steroidogenesis in vitro

DA CUÑA, RODRIGO; RODRIGUEZ, ENRIQUE; LO NOSTRO, FABIANA L.

Glasgow, Escocia

Congreso; 23rd Annual Meeting of the Society of Environmental Toxicology and Chemistry (SETAC Europe).; 2013

SETAC Europa

The use of the organochlorine insecticide endosulfan (ES) is in the process of being phased out worldwide after its inclusion in the list of Persistent Organic Chemicals by the Stockholm Convention. However, it is still used extensively in several countries as a broad spectrum insecticide in crops of high commercial value despite showing high toxicity to non-target animals and acting as an endocrine disruptor in fish. Our previous studies with the South American freshwater cichlid fish Cichlasoma dimerus showed waterborne exposure to ES (active ingredient; AI) caused decreased FSH pituitary content and histopathological alterations in testes.The aim of this study was to analyze and compare the in vitro effect of two commercial formulations (CF) of ES (Master® and Zebra Ciagro®) and the AI alone on gonadal steroidogenesis of C. dimerus to narrow down possible points of disruption. Testes and ovaries from adult fish were dissected and divided into equal pieces. Portions from the same gonad were randomly assigned to one experimental condition and incubated for 4 h in Krebs medium with the addition of DMSO (control), ES 100 M, LH 0.5 g/mL, ES 100 M + LH 0.5 g/mL, dehydroepiandrosterone (DHEA) 1 M or ES 100 M + DHEA 1 M. Testosterone (T) and estradiol (E2) levels were measured in media from incubated testes or ovaries using RIA or EQLIA, respectively. ES alone had no effect on T or E2 levels, either when using the CF or the AI. LH caused an increase in the synthesis and release of both sex steroids. The co-incubation of LH with ES -for both CF and the AI- caused a reduction in the level of sex hormones when compared with LH alone. When incubating with the 3HSD enzyme substrate DHEA, precursor in the biosynthetic pathway of both T and E2, a marked increase in both steroids was observed. Joint incubation of DHEA with ES -either CF or the AI- inhibited the increase in T and E2 when compared with DHEA alone. Based on these results, ES is capable of inhibiting the production of sex steroids from testes and ovaries in vitro, thus acting as an endocrine disruptor. As ES shows an inhibitory effect even when adding DHEA, it is likely to act downstream the synthetic pathway -e.i. interfering with 3HSD or 17HSD. No differences were found between the use of the AI alone or in combination with excipients in either CF, suggesting that the effect on steroidogenesis (Leydig or thecal cells) is caused by ES and not the remaining components of the mixture.