ENRICHMENT AND OXIDATIVE STRESS CHARACTERISTICS OF CD²⁺ IN LITOPENAEUS VANNAMEI IN AQUEOUS ENVIRONMENT

This study explored the enrichment and metabolism process, subcellular distribution characteristics and oxidative stress effect of heavy metal cadmium (Cd) in crustacean marine products in aqueous environment. Litopenaeus vannamei was used as the research object in this experiment. The enrichment phase of Cd in different exposure levels and pollution release in natural clean seawater were set up by two-box dynamic model. Both Cd content and the enzyme activity of glutathione S-transferase (GST), glutathione peroxidase (GPx) and catalase (CAT) in viscera and muscle tissues of Litopenaeus vannamei were monitored in real time. At the same time, the subcellular distribution characteristics of Cd enriched in viscera were analyzed by method of differential centrifugation. The results showed that the Cd enrichment in Litopenaeus vannamei was significantly positively correlated with the exposure levels in aqueous environment. Viscera was the most important tissue for Cd absorption and metabolism in Litopenaeus vannamei. The Cd absorption rate, purification rate, bioaccumulation factor and Cd content in equilibrium state were significantly higher than those in muscle tissue. Under the same exposure dose, the bioaccumulation factor of the Viscera was 75.5 times that of muscle, and the half-life of Cd in muscle tissue was significantly longer than that in visceral tissue. Cd was mainly stored in metallothionein-like protein (MTLP) and cell debris (CD) components, and a small part of Cd existed in organelle (ORG), metal-rich granules (MRG) and heat sensitive protein (HSP). With the continuous enrichment process, the percentage of Cd content in MTLP, ORG and HSP increased gradually, and the percentage of Cd content in CD and MRG decreased gradually. The activities of GST, GPx and CAT in liver and muscle tissues continued to increase significantly at the Cd enrichment stage, and decreased at the purification and release stage. Under the same experimental group, the activities of antioxidant enzymes in liver tissues were significantly higher than those in corresponding muscle tissues. This study aims to elaborate the enrichment and distribution characteristics of Cd in marine crustacean in the environment, preliminarily understand the possible mechanism of Cd enrichment, and provided scientific basis for risk assessment and environmental control of Cd pollution in marine crustacean.