| Summary: | 碩士 === 國立海洋大學 === 食品科學系 === 87 === Abstract
Common carp (Cyprinus carpio) has extraordinarily high zinc concentrations (300-500 g/g fresh tissue) in its digestive tract tissue, the fish also has high zinc concentration (usually＞100 g/g fresh tissue) in kidney, hepatopancreas and spleen. Zinc concentration of other aquatic organisms were in the level of 20 to 100 g/g fresh tissue. In order to understand whether the phenomenon also exist in its related species, e.g., crucian carp and goldfish, biochemical properties of zinc and zinc binding substances in the tissues of common carp, crucian carp and goldfish of Cyprinae of Cyprinidae, grass carp of Leuciscinae and silver carp of Hypophthalmichthyinae of the same family, and other fishes were examined.
It was found that in Cyprinidae fishes, zinc concentrations of the digestive tract tissue of common carp, crucian carp and goldfish were about 20 times higher than those of other fishes; and kidney, spleen and hepatopancreas were about 2 times higher than those of other fishes. Zinc in subcellular fractions of tissues of common carp, crucian carp and goldfish mainly existed in the nuclei/cell debris fraction. Metallothionein-like substance were found in the cytosol of hepatopancreas of Cyprinidae fishes (crucian carp, goldfish, grass carp and silver carp), but the amount in common carp was very little. High correlation between the zinc concentrations of nuclei/cell debris fraction and total tissue of common carp, crucian carp and goldfish tissue was found. Besides, grass carp, silver carp and tilapia tissues also have the some kind of relationship. In result, zinc concentrations in the whole tissue and nuclei/cell debris fraction are related.
The Debris Fraction of fish tissues was prepared by washing nuclei/cell debris fraction with 0.05 M Tris-HCl buffer pH 8.0. High correlation between the concentration of EDTA extractable-Zn and total tissue of common carp tissue, crucian carp and goldfish digestive tract tissues was found. The concentration of Total-SH and Free-SH in the Debris Fraction of digestive tract tissues of common carp, crucian carp and goldfish were measured. High correlation between the concentration of EDTA extractable-Zn and Bound-SH in the Debris Fraction of digestive tract tissues of common carp tissue, crucian carp and goldfish was found (r=0.94); this kind of correlation, however, was not found in grass carp, silver carp and tilapia. In digestive tract tissues of spotted chub mackerel, mackerel scad, kurma prawn and giant tiger prawn, high concentration of Total-SH was found, but there is little Bound-SH. The EDTA extractable-Zn are also very low, it is likely not correlation between Bound-SH and EDTA extractable-Zn concentration.
Based on the experiments, high concentration of Zn in the digestive tract tissue seems to be a characteristics of Cyprinae fish, and the Zn might be bound in membrane protein of Debris Fraction. The Lubrol Extract of digestive tract tissues of common carp, crucian carp and goldfish were separated by IMAC. The IMAC-adsorbed proteins of digestive tract tissue of common carp, crucian carp and goldfish were compared on SDS-PAGE. It was found that crucian carp and goldfish also have ZnSBMP (zinc specific binding membrane proteins) same as common carp. Same three bands of ZnSBMP were also found in other tissues of common carp, but the concentration and composition percentage were different. In Marine fish, spotted chub mackerel, mackerel scad and scad also exist some of the bands of ZnSBMP.
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