STUDIES ON STRESS RESPONSE OF AQUATIC ORGANISMS AND ASSESSMENT OF EFFECTS OF AQUATIC FACTORS THROUGH FOOD CHAIN

为了系统地研究水生生物对环境因子的响应，本研究以砷酸盐为模型化合物，研究了水环境中化学物质对水生生物的影响及其相关基因的表达。抗性菌株很少积累砷。在抗性菌株AR 3中，缺失了一部分竞争性结合砷酸盐的低亲和力磷酸盐转运蛋白，阐明了砷在多种水生生物中诱导甲基化。将砷掺入率高的菌株与砷共同孵育，用GC-MS分析有机砷，在该菌株中检测到二甲基砷。2）为了研究摇蚊对砷的抗性机制，对摇蚊的砷掺入进行了研究。经0.5mM砷酸盐处理后，体砷在孵育6小时时达到最大值，随后逐渐下降。用1.0mM砷酸盐孵育导致相当小的砷含量。摇蚊体内未检出甲基化砷化合物。这些结果表明，除了甲基化作用外，该物种还存在其他解毒机制。砷的主要化合物砷甜菜碱在肌肉中被微生物降解为氧化三甲基砷。

In order to detect systematically responses of aquatic organisms to environmental factors effects of chemicals in the aquatic environment and genes expressed by those factors were studied using arsenate as a model chemical.1) High sensitive and resistant strains of Clamydomonas were isolated by using random insertion mutation method. The resistant strains scarecely accumulated arsenic. In the case of resistant strain, AR3, deleted a part of low affinity-phosphate transportor which incorporates competitively arsenate.It has been clarified that arsenic induces methylation in various kinds of aquatic organisms. The strain with high rate of incorporation of arsenate was incubated with arsenic and organic arsenic was analyzed by GC-MS.Dimethyl arsenic was detected in this Clamydomonas.2)In order to examine the mechanism of resistancy against arsenate incorporation of arsenate into Chironomus was examined. Upon treatment with 0.5mM arsenate body arsenic reached maximum at 6hr of incubation followed by gradual decrease. Incubation with 1.0mM arsenate resulted in rather small arsenic content. In Chironomus methylated arsenic compund was not detected. These results suggest that some detoxic mechanism other than methylation operates in this species.3)In marine mullusca arsenic is accumulated abundantly. Major arsenic compound, arsenobetaine was degraded by microorganisms into trimethylarsine oxide in the muscle of this organism.