Comparison of NADH-dependent cytochrome b5 reductase activity and in vitro methemoglobin induction by sodium nitrite in Oncorhynchus mykiss, Salmo salar, and Salvelinus fontinalis

作者：McConkey Sandra^*; Saunders Janet; Speare David J

来源：Fish Physiology and Biochemistry, 2013, 39(3): 713-719.

DOI：10.1007/s10695-012-9734-x

• Methemoglobin
• Fish
• Cytochrome b5 reductase
• Oxidation

Methemoglobin is hemoglobin containing ferric iron. Methemoglobin cannot bind to oxygen and at high concentrations causes tissue hypoxia. Brook trout (Salvelinus fontinalis) develop significantly greater methemoglobinemia than Atlantic salmon (Salmo salar) or rainbow trout (Oncorhynchus mykiss) following general anesthesia with benzocaine or tricaine methanesulfonate. The objective of this study was to compare the activity of the major methemoglobin reducing enzyme, NADH-dependent cytochrome b5 reductase (CB5R), in brook trout erythrocytes to the activity of CB5R in Atlantic salmon and rainbow trout erythrocytes. Methemoglobin levels were compared using co-oximetry following in vitro incubation of erythrocytes with sodium nitrite (NaNO2). The CB5R activity was measured using a ferricyanide assay. There was significantly greater methemoglobin at time 0 in brook trout erythrocytes than in rainbow trout or Atlantic salmon erythrocytes (2.79 +/- A 0.29 %, 2.19 +/- A 0.23 %, 2.08 +/- A 0.14 %), (P < 0.001). There was significantly greater methemoglobin induction by NaNO2 in brook trout erythrocytes (33.14 +/- A 3.32 %) than in rainbow trout or Atlantic salmon erythrocytes (28.73 +/- A 2.92 % and 24.85 +/- A 1.40 %, respectively), (P < 0.001). The CB5R activity was significantly less in brook trout erythrocytes (median of 3.05 mu mol/min/mu l) than in rainbow trout erythrocytes (median of 6.73 mu mol/min/mu l). The CB5R activity in Atlantic salmon erythrocytes (median 4.09 mu mol/min/mu l) was not significantly different than in brook or rainbow trout erythrocytes. Total methemoglobin at any one time is a balance between induction by oxidants and reduction by antioxidants. Lower CB5R activity in brook trout erythrocytes may contribute to a species-specific sensitivity to methemoglobin induction; however, there are likely additional factors.

• 出版日期2013-6