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Key Event Title
Reduction, Vitellogenin accumulation into oocytes and oocyte growth/development
|Level of Biological Organization|
Key Event Components
Key Event Overview
AOPs Including This Key Event
|AOP Name||Role of event in AOP||Point of Contact||Author Status||OECD Status|
|Aromatase inhibition leading to reproductive dysfunction||KeyEvent||Cataia Ives (send email)||Open for citation & comment||WPHA/WNT Endorsed|
|Androgen receptor agonism leading to reproductive dysfunction||KeyEvent||Evgeniia Kazymova (send email)||Open for citation & comment||WPHA/WNT Endorsed|
|Estrogen receptor antagonism leading to reproductive dysfunction||KeyEvent||Evgeniia Kazymova (send email)||Open for citation & comment||EAGMST Under Review|
|Prolyl hydroxylase inhibition||KeyEvent||Allie Always (send email)||Under Development: Contributions and Comments Welcome|
|Unknown MIE leading to reprodl||KeyEvent||Evgeniia Kazymova (send email)||Under Development: Contributions and Comments Welcome|
|AHR mediated epigenetic reproductive failure||KeyEvent||Arthur Author (send email)||Under development: Not open for comment. Do not cite|
|Adult, reproductively mature||High|
Key Event Description
Vitellogenin from the blood is selectively taken up by competent oocytes via receptor-mediated endocytosis. Although vitellogenin receptors mediate the uptake, opening of intercellular channels through the follicular layers to the oocyte surface as the oocyte reaches a “critical” size is thought to be a key trigger in allowing vitellogenin uptake (Tyler and Sumpter 1996). Once critical size is achieved, concentrations in the plasma and temperature are thought to impose the primary limits on uptake (Tyler and Sumpter 1996). Uptake of vitellogenin into oocytes causes considerable oocyte growth during vitellogenesis, accounting for up to 95% of the final egg size in many fish (Tyler and Sumpter 1996). Given the central role of vitellogenesis in oocyte maturation, vitellogenin accumulation is a prominent feature used in histological staging of oocytes (e.g., (Leino et al. 2005; Wolf et al. 2004).
How It Is Measured or Detected
Relative vitellogenin accumulation can be evaluated qualitatively using routine histological approaches (Leino et al. 2005; Wolf et al. 2004). Oocyte size can be evaluated qualitatively or quantitatively using routine histological and light microscopy and/or imaging approaches.
Domain of Applicability
Oviparous vertebrates and invertebrates. Although hormonal regulation of vitellogenin synthesis and mechanisms of vitellogenin transport from the site of synthesis to the ovary vary between vertebrates and invertebrates (Wahli 1988), in both vertebrates and invertebrates, vitellogenin is incorporated into oocytes and cleaved to form yolk proteins.
- Leino R, Jensen K, Ankley G. 2005. Gonadal histology and characteristic histopathology associated with endocrine disruption in the adult fathead minnow. Environmental Toxicology and Pharmacology 19: 85-98.
- Tyler C, Sumpter J. 1996. Oocyte growth and development in teleosts. Reviews in Fish Biology and Fisheries 6: 287-318.
- Wolf JC, Dietrich DR, Friederich U, Caunter J, Brown AR. 2004. Qualitative and quantitative histomorphologic assessment of fathead minnow Pimephales promelas gonads as an endpoint for evaluating endocrine-active compounds: a pilot methodology study. Toxicol Pathol 32(5): 600-612.