Event Title

The oxidative degradation of hemoglobin in coho, chinook, pink and chum salmon

Presentation Abstract

Urban runoff contains a complex mixture of anthropogenically-sourced contaminants that can elicit symptoms of cardio-respiratory distress and acute mortality in coho salmon. Road runoff from high traffic areas has been implicated as a specific source of contaminants triggering these symptoms in coho. Effect-based water quality assessments have demonstrated that road runoff can induce oxidative stress. The oxidation of hemoglobin produces methemoglobin, which is incapable of binding oxygen unless reduced by the antioxidant system of a red cell. However, upon ligation to an amino acid site along the globin chain, methemoglobin is converted to hemichrome, which is typically followed by rapid precipitation, resulting in permanent loss of oxygen transport ability. Although spontaneous hemichrome formation is not typical of mammalian hemoglobins without prior structural alteration, it has been demonstrated to occur in some fish species. Due to the apparent instability of coho methemoglobin, we postulated that hemichrome formation and precipitation might occur subsequent to methemoglobin formation in coho. Using a chemical regression modeling technique based on the pseudo-first order reaction of the conversion of methemoglobin to hemichrome, we determined the rate constants and fractions of hemichrome-forming hemoglobins for coho, chinook, pink and chum salmon. We found that all four species of salmon demonstrated significant fractions of hemichrome-forming hemoglobin (30% - 50%) with first-order rate constants in the range of 0.0022 – 0.0033 s-1. We conclude that spontaneous hemichrome formation and hemoglobin precipitation is likely to be common in these species when exposed to oxidative stress. Although these four species may similarly experience some level of hypoxic stress through the oxidative degradation of their hemoglobin upon exposure to road runoff, their compensatory responses may be variable and some may exacerbate the induction of oxidative stress. Coho may therefore be an important indicator species for sublethal effects of oxidative stress in other aquatic organisms.

Session Title

Biological Indicators of Stormwater Impacts and Mitigation Effectiveness in the Salish Sea

Conference Track

SSE3: Fate, Transport, and Toxicity of Chemicals

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE3-509

Start Date

6-4-2018 9:00 AM

End Date

6-4-2018 9:15 AM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 6th, 9:00 AM Apr 6th, 9:15 AM

The oxidative degradation of hemoglobin in coho, chinook, pink and chum salmon

Urban runoff contains a complex mixture of anthropogenically-sourced contaminants that can elicit symptoms of cardio-respiratory distress and acute mortality in coho salmon. Road runoff from high traffic areas has been implicated as a specific source of contaminants triggering these symptoms in coho. Effect-based water quality assessments have demonstrated that road runoff can induce oxidative stress. The oxidation of hemoglobin produces methemoglobin, which is incapable of binding oxygen unless reduced by the antioxidant system of a red cell. However, upon ligation to an amino acid site along the globin chain, methemoglobin is converted to hemichrome, which is typically followed by rapid precipitation, resulting in permanent loss of oxygen transport ability. Although spontaneous hemichrome formation is not typical of mammalian hemoglobins without prior structural alteration, it has been demonstrated to occur in some fish species. Due to the apparent instability of coho methemoglobin, we postulated that hemichrome formation and precipitation might occur subsequent to methemoglobin formation in coho. Using a chemical regression modeling technique based on the pseudo-first order reaction of the conversion of methemoglobin to hemichrome, we determined the rate constants and fractions of hemichrome-forming hemoglobins for coho, chinook, pink and chum salmon. We found that all four species of salmon demonstrated significant fractions of hemichrome-forming hemoglobin (30% - 50%) with first-order rate constants in the range of 0.0022 – 0.0033 s-1. We conclude that spontaneous hemichrome formation and hemoglobin precipitation is likely to be common in these species when exposed to oxidative stress. Although these four species may similarly experience some level of hypoxic stress through the oxidative degradation of their hemoglobin upon exposure to road runoff, their compensatory responses may be variable and some may exacerbate the induction of oxidative stress. Coho may therefore be an important indicator species for sublethal effects of oxidative stress in other aquatic organisms.