Chapter 16 Vitellogenesis and endocrine disruption

Vitellogenesis and choriogenesis in fishes

“…The process or period in which this Vtg-derived egg yolk accumulates within oocytes is called vitellogenesis. During this process, estrogen secreted from the ovarian follicles triggers the synthesis of Vtg in the liver, which is then secreted into the blood, incorporated into oocytes and cleaved to generate multiple egg yolk proteins such as lipovitellin (Lv) and phosvitin (Pv) that will be stored in the ooplasm (reviews in Wallace [17], Mommsen and Walsh [18], Selman and Wallace [19], Specker and Sullivan [20], Hiramatsu et al [21,22], Patiño and Sullivan [23], Reading and Sullivan [24]). …”

Probing the xeno-oestrogenic impact of sediment cores contaminated by the pulp and paper industry: induction of aromatase cyp19a1b in late larval zebrafish

“…A part of vertebrate endocrine signalling is based on the response to endogenous steroids (androgens and estrogens) that occupy receptors that initiate a cascade of processes, eventually leading to the activation of respective steroid-responsive genes prior to the production of phenotype-specific proteins (Hiramatsu et al 2005) (Fig. 1).…”

“…P450scc, cytochrome P450 side-chain cleavage; Cyp17, cytochrome P450 17 -hydroxylase/17, 20-lyase; 3 -HSD, 3 -hydroxysteroid dehydrogenase; 17 -HSD, 17 -hydroxysteroid dehydrogenase; ERE, estrogen receptor element; Vtg, vitellogenin; Zrp, zona radiata protein; Hsp90, heat shock protein 90. Depicted according to several sources (Baroiller et al 1999, Carvan et al 2005, Hiramatsu et al 2005, Thomas 2008). …”

“…Nuclear receptors are a superfamily of transcription factors that are activated by binding ligands, both endogenous and exogenous, and mediate signaling over various gene networks (Hiramatsu et al 2005). Mode-of-action (MoA) of xenohormonal compounds that mimic endogenous steroids are mediated by binding to steroid receptors, a subfamily of nuclear receptors.…”

“…The presence of Vtg, normally occurring in females, also in male fish, is known to be negatively correlated with testicular growth and maturation in adult fish (Jobling et al 1996). Classification of multiple teleost Vtgs (types A, B and C) was based on the composition of their protein domain structure (Hiramatsu et al 2002(Hiramatsu et al , 2005. Furthermore, the diversity of Vtg regulation in zebrafish alone, with at least seven Vtg genes, show age-, sex-, and tissue-dependent expressions, with vtg1 being the most pronouncedly expressed in the adult (Wang et al 2005) as well as in embryonic zebrafish, as early as 48 hpf when exposed to EE2 (Muncke and Eggen 2006).…”