Evaluation of co-oximetry for the measurement of methemoglobin in rainbow trout (Oncorhynchus mykiss) and values in 3 salmonid species
Version of Record online: 12 SEP 2012
© 2012 American Society for Veterinary Clinical Pathology
Veterinary Clinical Pathology
Volume 41, Issue 4, pages 471–477, December 2012
How to Cite
Saunders, J., Speare, D. J. and McConkey, S. (2012), Evaluation of co-oximetry for the measurement of methemoglobin in rainbow trout (Oncorhynchus mykiss) and values in 3 salmonid species. Veterinary Clinical Pathology, 41: 471–477. doi: 10.1111/j.1939-165X.2012.00466.x
- Issue online: 14 DEC 2012
- Version of Record online: 12 SEP 2012
- Atlantic Veterinary College
- Salmo salar ;
- Salvelinus fontinalis ;
Methemoglobin (metHb) is oxidized hemoglobin that cannot reversibly bind oxygen, and concentrations in healthy fish have been reported to be 0.6–24.8% compared with 0–3% in healthy mammals. In fish, metHb has been measured using spectrophotometric methods using potassium cyanide (KCN), but not using co-oximetry, which is the preferred method for human samples.
The aims of this study were to evaluate co-oximetry as a method for measuring metHb in Oncorhynchus mykiss, compare co-oximetry with a KCN spectrophotometric method, and establish reference values for metHb concentrations as measured using co-oximetry in O mykiss, Salmo salar, and Salvelinus fontinalis.
Blood samples from healthy female O mykiss, female S salar, and female and male S fontinalis were prepared by separation and washing of erythrocytes in Tris/NaCl/EDTA buffer followed by lysis in Tris/EDTA buffer. MetHb concentrations were measured using an IL-682 co-oximeter. Moderate and high metHb concentrations were produced in vitro using NaNO2.
At low concentrations of methemoglobin, CVs for intraday precision were 10.3% and 53.9% using co-oximetry and the KCN spectrophotometric method, respectively. The CV for interday precision using co-oximetry was 11.9%. MetHb concentrations were stable in whole blood stored at 4°C for 7 days. MetHb concentrations were linear up to 58.2% (r = .99) using co-oximetry and 27.5% (r = .94) using the KCN method. The lower limit of detection for metHb was 0.02 g/dL using co-oximetry. Reference values for metHb concentrations using co-oximetry in O mykiss, S salar, and S fontinalis (n = 40 of each species) were 0.6–1.8%, 1.1–1.9%, and 1.1–4.0%, respectively.
Co-oximetry can be used to measure methemoglobin in blood from fish, in particular in O mykiss, and is better than the KCN spectrophotometric method. Reference values for methemoglobin concentrations in O mykiss, S salar, and S fontinalis are similar to those in mammals.