Abstract
Summary Estradiol-17β (E2) plays an important role in the endocrine control of female reproduction. In vertebrates, it induces the synthesis of the yolk protein vitellogenin in hepatocytes. During oogenesis, vitellogenin is secreted into the blood and accumulates in the growing oocytes in yolk granules or platelets. In the polychaete Nereis virens, vitellogenin is secreted by specialized coelomic cells called eleocytes during oogenesis. As the hormonal regulation of vitellogenesis is poorly understood in annelids, this investigation focuses on estrogen signalling in N. virens. Coelomic fluid samples of females, males and juveniles were analysed for E2 concentrations by enzyme immuno assay (EIA). E2 was present at a concentration of 20.03 ± 11.79 pg.ml−1 (n= 15) averaged over all stages. Western blots revealed a putative estrogen receptor protein of around 60 kDa in eleocytes from young females at the onset of vitellogenesis. Finally, the steroidogenic enzyme 5,3β-hydroxysteroid dehydrogenase (3β-HSD) was detected in the gut epithelium by histochemistry. Our results suggest that E2 plays a role at an early stage of oogenesis by activating the expression of vitellogenin in the eleocytes. We suggest that the sites of steroid synthesis are probably the gut epithelium and eleocytes of N. virens.
Published Version
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