Mechanisms involved in cadmium toxification on tilapia larva (oreochromis mossambicus)

• Main Authors: Yu, Ming Jun, 余明俊
• Other Authors: Huang, Peng Peng
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/01027874569950430794

碩士 === 國立臺灣大學 === 漁業科學研究所 === 83 === The effects of environmental Cd and calcium (Ca) on the mRNA expression of metallothionein (MT), Cd accumulation, calcium content and growth in tilapia larvae were examined. In tap water, high Cd concentration had lethal effect on tilapia larvae. The contents of Cd at 96 h was higher in 50 than 150 ug/l Cd treatments, which suggests that failure in self-protective function may lead to death. Both the contents of Cd and Ca of tilapia larvae in each treatment increased as larval growth. However, the contents of both Ca and Cd of larvae in 100 ug/l were less than those in 50 ug/l Cd treatment. Thus, high cadmium concentration may inhibit the Ca uptake of larvae, which is necessary for the normal growth of larvae. The MT cDNA sequence was cloned and the expression of the larval MT mRNA in various Cd concentration treatments were analyzed by northern blot hybridization. The expression of MT mRNA increased as the increasing Cd concentrations, which implied that the MT contributed to tilapia larvae the protective ability in preventing from Cd toxicity. The expression of MT needs to be studied further. Compared to the larvae in normal tap water ([Ca++]=0.1mM), the mortality of larvae in high-Ca ([Ca++}=2.0mM) water was much lower. Moreover, in high-Ca water, the Ca uptake and the total length of larvae were not inhibited by high Cd concentrations. These data suggested that high Ca concentration supplied a normal Ca uptake and growth of tilapia larvae, which may prevented the larvae from death. Our results indicated that Ca uptake plays a important role in normal growth of tilapia larvae. Cd competes with Ca for the entrance of Ca may lead to inhibition of growth and death. The interaction between Ca and Cd remains to be studied further.