博士 / 國立海洋大學 / 水產食品科學系 / 86 / Zinc concentrations in different tissues of 24 aquatic organisms were investigated. Common carp and crucian carp had extraordinarily high zinc concentrations of mean values, 562 and 634 ug/g fresh tissue in their digestive tract tissues, and high zinc concentrations in the tissues of kidney, gill, skeletal tissues and spleen of values usually larger than 100 ug/g fresh tissue, which were not seen in other species. The concentrations of Cu, Na, K, Ca and Mg in the digestive tract tissues of common carp and several freshwater fishes were found to be similar. High zinc was found to be specific to common carp. Common carp was reared from fry till adult fish with artificial feed containing 35 mg Zn/kg diet in laboratory for 937 days, the zinc concentrations in the whole body and digestive tract tissue of the fish were found to be consistently high throughout all the period. The anterior portion of digestive tract tissue of common carp had highest zinc concentration of 1,590 ug/g fresh tissue, then decreased gradually to the end portion, about 500 ug/g fresh tissue.
High zinc of 2,000 mg Zn/kg diet was fed to common carp, grass carp and tilapia for 8 weeks to compare the accumulation of zinc in the fish. It was found that accumulation of zinc from diet in grass carp and tilapia was quite low when compared to that in common carp. The largest difference occurred in digestive tract tissue. When common carp was fed 2,000 mg Zn/kg diet for 24 weeks, the fish accumulated zinc first in its digestive tract tissue, and the mean zinc concentration "saturated" after 4 weeks, maintained at a level of 1,500 ug/g fresh tissue until the end of experiment (24 weeks). The accumulated zinc in the digestive tract tissue of common carp could be released, when the diet was reduced to normal level (50 mg Zn/kg diet) or deficient level (4 mg Zn/kg diet) for 4 weeks. The zinc concentration in the digestive tract tissue of common caip maintained at a certain level, even when diet was reduced to 4 mg Zn/kg diet for 21 weeks. It is very possible that the digestive tract tissue of common carp is an important zinc reservoir.
Zinc concentrations in subcellular fractions of digestive tract tissue, hepatopancreas, spleen and kidney of common carp mainly existed in the nuclei/cell debris fraction; the percentages were 82, 88, 57 and 72, respectively. It was found that only 10-40% of zinc was in cytosol fraction and small amounts in the microsomal and mitochondrial fraction.
Common carp fed with 2,000 mg Zn/kg diet for 12 weeks, the digestive tract accumulated zinc mainly in nuclei/cell debris fraction, and partially in cytosol-LMF. Zinc concentrations in cytosol-HMF, microsome, and mitochondria/lysosome fraction were relatively unchanged throughout the experiment periods (12 weeks). The digestive tract tissue of common carp can accumulated zinc to 1,500 ug/g fresh tissue level, 75-80% of zinc in nuclei/cell debris fraction. Since there is little or no metallothionein in fish digestive tract tissue through Sephadex G-75 chromatography, it could be said that high concentration of zinc in common carp tissue is not likely derived from metallothionein.
The histological structure of digestive tract tissue of common carp consists of four basic layers: mucosa, subrnucosa, muscularis and serosa. Zinc was stained in the cell membrane of the mucosal epithelium, and also found evenly in the subrnucosal and muscular layers. Based on the zinc subcellular distribution data and histochemical staining, it seems that the digestive tract tissue having zinc is closely related to biomembranes.
| Identifer | oai:union.ndltd.org:TW/086NTOU3084001 |
| Date | January 1998 |
| Creators | 孫藍天 |
| Contributors | 鄭森雄 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 112 |
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