Effect of total isoflavones found in soybean on vitellogenin production in common carp

Balık diyetlerinde temel protein kaynağı olan balık ununun yerine soya fasulyesi yemi yaygın olarak kullanılmaktadır. Fakat soya fasulyesinin fitoestrojenik özellikleri balıklarda üremeyi etkileyeceğinden, diyetlerde soya fasulyesi bazlı yemlerin kullanılması endişe oluşturmaktadır. Bu çalışmanın amacı çeşitli konsantrasyonlarda hazırlanan toplam isoflavon içeren soya fasülyesi özütleri ile sazangil balıklarında vitellojenin proteini üretimi arasında bir ilişkinin olup olmadığını belirlemektir. Beş farklı dozda (içerdikleri toplam isofavon oranlarına göre 0, 250, 500, 1.000 ve 10.000 mg/kg) hazırlanan ticari soya fasulyesi özütleri fitoestrojen konsantrasyonlarının vitellojenin sentezine etkisini belirlemek için dişi ve erkek sazanda, Cyprinius carpio L., test edilmiştir. Bütün balık grupları içinde özütlerin büyümeye etkisinde herhangi bir farklılık bulunamamıştır. Soya özütlerinin bütün konsantrasyonları erkeklerde GSI değerini düşürmüş, fakat dişilerin GSI değerinde 500 mg/kg soya özütü konsantasyonuna kadar arttırmış daha sonra da yüksek dozlarda da düşürmüştür. Bu da plazma içindeki vitellojenin seviyesinin inhibisyonu ve indüklenmesi ile ilişkilendirilmiştir. GSI ve vitellojenin değerindeki değişikliklerin, fitoestrojenlere maruz kalan bireyleri belirleyebilecek hassas bir belirteç olduğunu ortaya çıkarmıştır. Daha yüksek dozlardaki isoflavonlar her iki cinsiyetteki balıklar için daha fazla vitellojenin üretmiştir. Bu çalışma sonucunda fitoestrojen içeren soya fasulyesi özütleriyle hazırlanan yemlerle beslenen her iki cinsiyetteki balıkların vitellojenin üretiminin indüklenmesi açıkça gösterilmiştir. GSI değerleri ve yüksek oranda vitellojenin üretimi, fitoestrojen içeren soya fasulyesinin balıkların endokrin sistemlerinde tahrip edici etkisi olduğunu işaret etmiştir. Balık yemlerinin hazırlanmasında, endokrin bozucu etkiye sahip olan soya fasulyesi ürünlerinin kullanımı dikkate alınması gereken bir husus olmalıdır.

Anahtar Kelimeler:

bitkisel östrojenler, yumurta sarısı oluşumu, balık beslenmesi, soya fasulyesi, sazan balığı, gonadosomatik indeks

Soya fasulyesinde bulunan toplam isoflavonların sazan balıklarında vitellojenin üretimine etkisi

Soybean meal is used most extensively as a replacement to fishmeal as the main protein source in fish diets. However, there is concern about the effect of soybean-based diets on reproductive development of the fish because of the phytoestrogenic properties of soybean. The objective of the present study was to determine whether a relationship exists between the concentration of soybean extract containing total isoflavones in diet and the production of vitellogenin protein in cyprinid fish. Five different doses (0, 250, 500, 1.000, and 10.000 mg/kg based on total isoflavones content) of commercial soybean extract were tested to determine the effect of pyhtoestrogens concentration on vitellogenin synthesis in female and male carp, Cyprinius carpio L. There were no significant differences in the growth of fish between any of the groups. All concentrations of soybean extract lowered male gonadosomatic index (GSI), but female GSI was increased in diets including up to 500 mg/kg soybean extract, and then decreased at higher doses. This was associated by an inhibition and induction, respectively, in plasma vitellogenin levels. Changes in GSI and vitellogenin appeared to be sensitive marker for detecting phytoestrogens exposure. Higher concentrations of isoflavones resulted in a higher amount of vitellogenin produced in both male and female fish. Our results clearly showed that exposure to phytoestrogens found in soybean extract significantly induces vitellogenin production in both males and females, in a dose-response manner. GSI and high vitellogenin production indicated that phytoestrogens found in soybean disrupt the endocrine system of fish. The endocrine disruptor effect of soybean products must be considered in fish meal preparation.

Keywords:

plant oestrogens, vitellogenesis, fish feeding, soyabeans, carp, gonadosomatic index,

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