Evaluation of the accumulation of Cd, Pb and their impact on the endocrine system as well as the detoxification mechanism of these metals in Climbing Perch (Anabas testudineus)

Theoretical results: The 96 h LC50 values of Pb and Cd for A. testudineus were found to be approximately 120 and 38 mg/L, respectively. To study the accumulation of Pb and Cd in the body and assess the effects of these metals on the endocrine system, healthy A. testudineus were exposed to Pb (20, 30, and 40 mg/L) and Cd (3, 5, and 10 mg/L) for seven, 14, 21, and 28 days. The order of Pb accumulation in the tissues after exposure was gill >> liver > muscle whereas the order of Cd accumulation was liver >> gill > muscle. Endocrine dysfunction was characterized by varying the levels of cortisol, glucose, insulin plasma and liver glycogen levels. Exposure to both Pb and Cd caused a significantly increase levels of cortisol in plasma (p < 0.05), while plasma glucose levels slightly increased at the beginning and then decreased sharply. Glucose in the blood is generated from the breakdown of carbohydrates from food in the small intestine and the breakdown of stored glycogen in the liver. Liver glycogen levels in fish exposed to Pb and Cd were significantly decreased as time proceeds. Since glucose in the blood is used to provide energy for the whole body, to maintain normal plasma glucose levels during starvation, the liver acts an important role in the production of glucose through glycogenolysis and gluconeogenesis. In addition, plasma insulin levels in fish exposed to Pb and Cd were significantly reduced to depletion. Insulin depletion interferes with glycogen storage in the liver and muscle of fish. K+/Na+-ATPase is a membrane bound enzyme located mostly in osmoregulatory tissues such as gill and intestine where it maintains ionic and electrical gradients necessary for transepithelial salt movements. The decrease in K+/Na+-ATPase enzyme activity on gills of fish living in Pb and Cd could be related to high affinity of these metals to –SH groups on the enzyme molecule, membrane rupture, osmoregulation dysfunctions, or disturbance of the ion homeostasis, leading to affect some important metabolism in the organism. Organic Pb compounds are more toxic than inorganic Pb, the conversion from inorganic Pb to organic Pb in the liver and muscle of A. testudineus was relatively low. About 55% Cd in liver and  80% Cd in muscle of  A. testudineus is bound to metallothionein as a protective mechanism for the body from the toxicity of Cd.
Applied results: The results of this study will provide a scientific information for basic research in the field of aquatic toxicology to assess the impact of pollutants in water on the endocrine system including the pancreas, adrenal glands, etc and response of individual fish species to each pollutant.

It has been found the order of accumulation of Pb and Cd as well as the effects of these metals on the endocrine system (pancreas, adrenal gland) of climbing perch.

- Scientific papers in referred journals (list): 01 on  SCI-E and 01 on national journal
•    SCI-E journal: Dang Nguyen Nha Khanh, Ngo Thi Tuong Vy, Tran Ha Phuong, Pham Tuan Nhi, Nguyen Quoc Thang, Do Trung Sy, Nguyen Thi Kim Phuong- Effects of Cadmium and Lead on Muscle and Liver Glycogen Levels of Climbing Perch (Anabas testudineus), Bulletin of Environmental Contamination and Toxicology, https://doi.org/10.1007/s00128-021-03384-4
•    National journal: Dang Nguyen Nha Khanh, Ngo Thi Tuong Vy, Tran Ha Phuong, Pham Tuan Nhi, Vu Quang Huy, Nguyen Quoc Thang, Do Trung Sy, Le Tien Dung, Nguyen Duy Khanh, Nguyen Thi Kim Phuong - Study on the accumulation and transformation of lead in liver and muscle of climbing perch (Anabas testudineus), Vietnam Journal of Catalysis and Adsorption (Acceptance letter on 14 october 2021).
- Patents (list): None
- Technological products (describe in details: technical characteristics, place): Products of this project are reports. The reports were stored at the Hochiminh Institute of Resource Geography, including:
• 05 reports about samples preparation and procedures of analysis for levels of cortisol, insulin and glucose in blood, level of glycogen in liver and level of K+/Na+-ATPase enzyme activity in gills of climbing perch.
• 02 reports about acute toxicity thresholds of Pb and Cd (LC50 96h) for climbing perch.
• 02 reports on the accumulation of Pb and Cd in gills, liver and muscle of climbing perch.
• 02 reports on the effects of Pb and Cd on the changes in levels of cortisol, insulin and glucose in blood.
• 02 reports on the effects of Pb and Cd on changes levels of glycogen in liver and K+/Na+-ATPase enzyme activity in gills.
• 02 reports on the detoxification mechanism of Pb and Cd (chemical conversion of Pb and Cd) in liver and muscle of climbing perch.
- Other products (if applicable): 1 PhD student

Aquatic and Water Quality Regulatory Authority, Aquatic Toxicologists.