Effect of Acute Hypoxia in Trout (Oncorhynchus mykiss) on Immature Erythrocyte Release and Production of Oxidative Radicals

• Published in: Fish physiology and biochemistry 2005-01, Vol.31 (1), p.65-72
• Main Authors: Valenzuela, A., Silva, V., Tarifeño, E., Klempau, A.
• Format: Article
• Language: English
• Subjects: Ammonium; Erythrocytes; Hypoxia; Oncorhynchus mykiss; Oxygen; Oxygen consumption; Salmon; Trout
• ISSN: 0920-1742; 1573-5168
• DOI: 10.1007/s10695-005-5288-5

This paper evaluates the response of trout exposed to acute hypoxia between 8.7 mgO^sub 2^/l (controls) and 1.4 mgO^sub 2^/l. Temperature, pH, NH4, oxygen consumption rate and spleen-somatic index (SSI) were evaluated. Blood cell counts, oxidative radicals (ORs) production and immature erythrocytes were assessed to evaluate their relationship with the degree of hypoxia. Acute hypoxia induced a decrease in water pH (p < 0.05), oxygen consumption rate (60% less), SSI (55% less) and a significant increase of water ammonium concentration (p < 0.05). Haematocrit increased significantly starting at 4.8 mgO^sub 2^/l, as well as an increase in the total number of leukocytes (up to 50% in some fish). Starting at 2 mgO^sub 2^/l, swelling of erythrocytes was induced and a decrease in the potential production of ORs, showing a negative correlation to immature erythrocyte numbers. These results suggest that lower than normal oxygen concentrations may jeopardize ORs production and hence non-specific defence mechanisms in trout. High percentages of immature erythrocytes can be used as a simple and inexpensive indicator of both hypoxic events and impairment of ORs production in the absence of bleeding, haemolysis, anti-anaemia treatments and/or increased temperature.[PUBLICATION ABSTRACT]