Effect Of Genistein On Digestive Enzymes And Antioxidant Systems Of Goldfish, Carassius Auratus

Genistein is an isoflavone found abundant in leguminous plants. It is structurally similar to mammalian estrogens and it is one of the most potent phytoestrogens in soybean and soy products. On the one hand, genistein congregate into the aquatic environments through various approaches. On the other hand, plant protein-based diets are also rich in genistein. All of these make fish being exposed to genistein through aquatic environments and dietary sources.By now, only few researches about the effects of genistein on fish existed in the literature. The previous work has known that the genistein may disturb the growth, procreation and normal behaviors of fish. However, there are some results diverge from them. So, It's necessary to do more comprehensive and in-depth researches to explain the impact modes and mechanisms of genistein on development, reproduction and behavior of fish.Goldfish(Carassius auratus) is small size freshwater fish, easy to rear and maintain in laboratory. In this paper, we selected genistein as experimental reagent and used goldfish as model animal. Adult goldfish were treated with 0.2, 2 and 20μg/g body weight of genistein by intraperitoneal injection. After 7 days, the induction of vitellogenin(VTG) and the level of plasma sex steroid hormones were determined to analysis the estrogenic effects of genistein. In addition, in order to provide basic data and reference for the effects of genistein on fish, we investigate the activities of digestive enzymes and antioxidant enzymes. The results showed that:(1) Following intraperitoneal injection of genistein(0.2, 2 and 20μg/g) for 7 days, the inductions of VTG in male goldfish were detected in all treatment groups. The native polyacrylamide gel electrophoresis (Native-PAGE) were stained by the methods of glycoprotein, phosphoprotein and lipoprotein staining, and the results showed that genistein induced VTG synthesis in male goldfish. After that, SDS-PAGE was used to detect the molecular weights of VTG. The result showed that the VTG has two main protein subunits with relative molecular weights of 130kDa and 83kDa, respectively. In addition, testosterone and estradiol concentrations in plasma were determined by radioimmunoassay(RIA). The concentrations of plasma testosterone decreased in all treatment male fish, while the estradiol increased, and the treatment level of 2μg/g genistein (middle) has the greatest magnitude of effect. The results proved that genistein has estrogenic activity in goldfish.(2) The activities of digestive enzymes are tight related with the growth performance of fish. This work has determined the effects of genistein on several digestive enzymes of goldfish. The results showed that there are significant decrease in both protease activities and amylase activities in goldfish liver and intestine than control following treatment by 2μg/g(P<0.05) and 20μg/g(P<0.01) genistein. The activities of intestinal alkaline phosphatase are significant decreased in all treatments. Obviously, genistein reduced the digestive enzymes activities, thus may have negative effect on growth performance of goldfish.(3) The activities of superoxide dismutase(SOD), catalase(CAT), glutathione S-transferase(GST) and the content of malondialdehyde (MDA) in goldfish liver were determined during the treatment process. The content of MDA increased with the time of treatment, and the activities of SOD increased significantly after 4 days(P<0.05) and 7 days(P<0.01), whereas the activities of CAT and GST were induced obviously at the first day. It is concluded that genistein caused the oxidation stress to goldfish, provoking the activites of antioxidant enzymes as a response to the pressure.In conclusion, using Native-PAGE and SDS-PAGE, this paper confirmed that gnistein induced the synthesize of VTG in male goldfish, interfered the production of testosterone and estradiol level, proving that it does serve as a phyoestrogen in goldfish. In addition, genistein reduced the activities of primary digestive enzymes remarkably and exert oxidation stress to goldfish indicating that genistein may affect the growth and normal physiological funtions of goldfish besides its estrogeinc effects.