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First published online June 29, 2007
Journal of Experimental Biology 210, 2574-2584 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.004028

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Cardiac remodelling in rainbow trout Oncorhynchus mykiss Walbaum in response to phenylhydrazine-induced anaemia

Danielle L. Simonot and Anthony P. Farrell^*

Department of Biological Sciences, 8888 University Drive, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada

^* Author for correspondence at present address: Department of Zoology and Faculty of Land and Food Systems, 6270 University Boulevard, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada (e-mail: farrellt{at}interchange.ubc.ca)

Accepted 2 May 2005

We examined the nature, extent and timing of cardiac ventricular remodelling in response to chronic, chemically induced anaemia in warm- and cold-acclimated rainbow trout Oncorhynchus mykiss. Chronic anaemia was induced by bi-weekly injections of phenylhydrazine hydrochloride (PHZ) and resulted in transient but large decreases in haematocrit (Hct) and haemoglobin concentration. After 2 weeks of anaemia, relative ventricular mass (rM_V) in warm-acclimated rainbow trout had already increased significantly and, by the eighth week of anaemia, rM_V was 58% greater than in the sham-injected control fish. Temperature modulated the anaemia-induced ventricular remodelling and erythropoietic responses, as indicated by cold-acclimation reducing the extent of the cardiac remodelling and slowing erythropoietic recovery. For example, in cold-acclimated fish, PHZ reduced Hct to 8.8±1.9% (ranging from 4–16%) and increased rM_V by 15% over a 4-week period, whereas the same treatment in warm-acclimated fish reduced Hct to only 17.4±2.1% (ranging from 6–29%) and yet increased rM_V by 28%. Cold-acclimated fish also recovered more slowly from anaemia. In addition, warm-acclimated fish maintained compact myocardium between 32% and 37% during anaemia, while cold-acclimated fish responded with an increase in compact myocardium (from 29% to 37%). Routine cardiac output () was continuously monitored following a single PHZ injection to examine the initial cardiac response to anaemia. Contrary to expectations, acute anaemia did not produce an immediate, proportionate increase in routine . In fact, did not increase significantly until Hct had decreased to 10%, suggesting that rainbow trout may initially rely on venous oxygen stores to compensate for a reduced arterial oxygen-carrying capacity. Thus, we conclude that myocardial oxygenation, acclimation temperature and cardiac work load could all influence anaemia-induced cardiac remodelling in rainbow trout.

Key words: cardiac remodelling, compact myocardium, anaemia, temperature acclimation, heart