Induction of Plasma Vitellogenin Synthesis by the Commercial Fish Diets in Male Goldfish(Carassius auratus) and Dietary Phytoestrogens.

Abstract

In this study, we analyzed contents of phytoestrogens (genistein, daidzein, equol, and coumestrol) in two commercial fish diets [a diet for trout (TD) and a diet for ornamental carp (CD)] using Liquid Chromatography-Mass Spectroscopy/Mass Spectroscopy (LC-MS/MS), and these contents were compared with that of a casein-based formulated fish diet (FD) which does not contain soya bean or fish meal. We also analyzed phytoestrogen contents in commercial infant casein-and soya bean-based diets. The contents of phytoestorogens were generally high in CD, TD, and soya milk, and low or non-detectable in FD and casein-based milks. Among these samples, CD showed the highest phytoestrogen contents: genistein, 390800 ng/g; daidzein, 416800 ng/g; coumestrol, 1325 ng/g; equol, 6.4 ng/ g. We also determined the estrogenic activity of the fish diets using male goldfish by measuring plasma vitellogenin (VTG) levels as a biomarker of estrogen exposure. When male goldfish were fed one of these diets for 31 days, plasma VTG was detected in CD-fed fish (78.01 ± 48.18 µg/ml) and TD-fed fish (3.51 ± 3.83 µg/ml), whereas plasma VTG was not detected in FD-fed fish (less than 0.040 µg/ml). These results indicate that the commercial fish diets examined contain a large amount of phytoestrogens and showed estrogenic activity that were strong enough to induce VTG production in male goldfish. It is necessary to eliminate estrogenic substances other than test chemicals in the screening test system for estrogenic endocrine-disrupting chemicals (EDCs). Since the formulated diet developed in the present study contain less phytoestrogens than the commercial fish diets and has low estrogenic activity, it is suggested that VTG production using male goldfish in combination with the low estrogen fish diet is a good in vivo system for evaluation of estrogenic effects of EDCs.

The Potential Contribution of Phytoestrogens and Organochlorine Pesticides in an Experimental Fish Diet to Estrogenic Activity

“…22) Moreover, we reported that plasma Vg was detected in male goldfish fed 1.0% body weight of the diet containing phytoestrogens (genistein, 47.7 µg/g; daidzein, 41.1 µg/g) every two days for 31 days. 28) In the present study, genistein (concentrations ranging from 39.7 to 118.9 µg/g) and daidzein (concentrations ranging from 28.7 to 81.3 µg/g) were detected in all fish diets. These dietary concentrations of phytoestrogens with the exception of the No.…”

Estrogenic activity of tropical fish food can alter baseline vitellogenin concentrations in male fathead minnow (Pimephales promelas)

“…Other species of fish have also been shown to experience diet-induced increases in the plasma VTG concentration, caused by sex steroids and/or phytoestrogens in the diet, including tilapia [10], goldfish [29,30], medaka [31], and carp [32]. No studies have, however, been carried out on commonly available tropical fish diets or with fathead minnows.…”

Development of Plasma Vitellogenin Assay for Estrogenic Effects of Endocrine-Disrupting Chemicals Using Ovariectomized Goldfish (Carassius auratus)

“…These ovariectomized, shamoperated, and unoperated female goldfish were not fed for a month before the start of the experiment, and were kept in a 25-l glass tank under natural conditions, as in the previous study. 10) Fish diets used in this study were a diet for ornamental carp (CD) and a newly developed casein-based formulated diet "No. 2," which does not contain soybean or fish meal.…”

“…In our previous study, the phytoestrogen content of CD was shown to be much higher than that in FD, and fish fed the CD diet had significantly higher VTG levels than the fish fed FD based on the plasma VTG assay of male goldfish. 10) Ovariectomized (6 fish, 2 groups), unoperated goldfish (4 fish, 2 groups), and sham-operated (4 fish, 1 groups) were fed 1.0% body weight volume of one of the two diets, FD or CD every 2 days for 31 days between May and June 2000. During the experimental period, the fish were maintained in dechlorinated tap water in 25-l glass tanks at 23-26°C under a 12 hr light-12 hr dark photoperiod.…”

“…9) In our previous study, we demonstrated significant increased plasma vitellogenin (VTG, egg yolk protein precursor) in male goldfish fed the phytoestrogenenriched fish diet (FD). 10) Recently, various screening and testing systems for EDCs in fish have been established through cooperation of the Organization for Economic Cooperation and Development (OECD) and U.S. Environmental Protection Agency (EPA). 11,12) Model test organisms include advanced fish strains such as fathead minnow (Pimephales promelas), zebrafish (Danio rerio) and Japanese medaka (Oryzias latipes).…”