Histopathology as a Tool for the Evaluation of Endocrine Disruption in Zebrafish (Danio Rerio)

Abstract

The importance of histology as a tool in the evaluation of endocrine disruption in fish depends on the choice and interpretation of appropriate endpoints, as is illustrated by the analysis of the effects of exposure to the estrogen 17beta-estradiol (E2) and the nonaromatizable androgen 17-methyldihydrotestosterone (MDHT). The E2 led to the disappearance of vitellogenic oocytes in the ovary and an increased area of relatively large, eosinophilic cells in the testis, which were identified as spermatogonia under high-power magnification; this was a relative increase, as was shown by histomorphometry, because of a decreased size of spermatogenic cysts and a relative decrease of spermatocyte cysts. The E2 also induced an accumulation of acidophilic fluid in vessels and interstitial spaces, confirmed by immunohistochemistry as vitellogenin, and basophilia in the liver also associated with the production of vitellogenin. The MDHT induced activation of Sertoli cells in the testis and a decreased presence of vitellogenic oocytes and a reduced growth of previtellogenic oocytes in the ovary. These observations indicate the advantages of examining multiple organ systems on whole-body sections and the application of adequate magnifications. Inclusion of additional techniques such as morphometry and immunohistochemistry is valuable to further uncover insidious effects of endocrine disruptors.

Influence of estradiol-17β, testosterone, and 11-ketotestosterone on testicular development, serum steroid hormone, and gonadotropin secretion in male red sea bream Pagrus major

“…Histological examination revealed that treatment with E2 inhibited meiotic division of spermatogonia. Similar inhibitory effects of E2 on testicular development have been reported in rainbow trout and in zebrafish showing that E2 inhibited testicular development and the progress from spermatogonia to spermatid 11,30 . Moreover, alkylphenolic compounds and synthetic estrogens such as nonylphenol, ethynylestradiol and octylphenol also had inhibitory effects on gonadal development in male teleost species 6–10 .…”

“…Recent studies reported that estradiol‐17β (E2), which is a natural estrogen but one of the strongest endocrine disruptors in the environment, and estrogenic compounds such as synthetic estrogen and alkylphenol, are discharged from sewage in several countries 3–5 . These estrogenic compounds have disrupted fish reproduction by causing an increase of vitellogenin in serum of male fish and inhibition of testicular development 5–11 . Additionally, exposure to pulp and paper mill effluent (PME) induced masculinization in female teleosts, suggesting that androgenic compounds were contained in PME 12–14 .…”

Estrogenic and androgenic effects of municipal wastewater effluent on reproductive endpoint biomarkers in three‐spined stickleback (Gasterosteus aculeatus)

“…The gonads can be considered as a primary target organ for exogenous compounds with estrogenic or androgenic activity. This also was observed in zebrafish exposed to 10 g/L of 17␣-methyl-dihydrotestosterone [33]. After the eggs are ovulated into the ovarian or peritoneal cavity, postovula-tory follicles remain for some time.…”

Effects of the estrogen agonist 17β‐estradiol and antagonist tamoxifen in a partial life‐cycle assay with zebrafish (Danio rerio)

“…Details regarding histotechnique and histological assessment have been described previously [14]. In brief, animals were fixed in Bouin's fixative for 24 h, then transferred and stored in 70% ethanol and embedded in paraffin after dehydration in a graded ethanol/xylene series.…”

“…Reproduction parameters (fecundity, fertility), mortality, and growth were evaluated and integrated with VTG expression and histology, with the latter enabling evaluation of the specific pathological events of endocrine disruption [14]. The online version was corrected 12/20/06.…”