The ionoregulatory responses to hypoxia in the freshwater rainbow trout oncorhynchus mykiss

Fathima I. Iftikar, Victoria Matey, Chris M. Wood

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

We utilized the rainbow trout, a hypoxia-intolerant freshwater teleost, to examine ionoregulatory changes at the gills during hypoxia. Progressive mild hypoxia led first to a significant elevation (by 21%) in JInflux Na (measured with 22Na), but at 4-h inf lux hypoxia when Po2 reached ∼110 mmHg, there was a 79% depression in J InfluxNa. Influx remained depressed during the first hour of normoxic recovery but was restored back to control rates thereafter; there were no significant changes in JeffluxNa or J netNa. A more prolonged (8 h) and severe hypoxic (∼80 mmHg) exposure induced a triphasic response whereby Jinflux Na was significantly elevated during the first hour, as during mild hypoxia, but returned to control rates during the subsequent 3 h. Thereafter, rates started to gradually increase and remained significantly elevated by about 38% through to 8 h of hypoxia. A similar triphasic trend was observed with JeffluxNa but with larger changes than in J influxNa, such that negative Na+ balance occurred during the hypoxic exposure. Net K+ loss rates to the water approximately doubled. There were no significant alterations in ammonia excretion rates in either of the hypoxia regimes. Branchial Na +/K+-ATPase activity did not change during 4 h at Po 2 ∼ 80 mmHg or return to normoxia; H+-ATPase activity also did not change during hypoxia but was significantly depressed by ∼75% after 6 h of normoxic recovery. Scanning electron microscopy revealed that within 1 h of exposure to Po2 ∼ 80 mmHg, exposed mitochondria-rich cell (MRC) numbers increased by 30%, while individual MRC exposed surface area and total MRC surface area both increased by three- to fourfold. MRC numbers had decreased below control levels by 4 h of hypoxia, but surface exposure remained elevated by approximately twofold, a response that persisted through 6 h of normoxic recovery. Environmental hypoxia induces complex changes in gill ionoregulatory function in this hypoxia-intolerant species that are very different from those recently reported in the hypoxia-tolerant Amazonian oscar.

Original languageEnglish
Pages (from-to)343-355
Number of pages13
JournalPhysiological and Biochemical Zoology
Volume83
Issue number2
DOIs
StatePublished - Mar 1 2010

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Mitochondria
Oncorhynchus mykiss
Fresh Water
hypoxia
Recovery
Proton-Translocating ATPases
Level control
mitochondria
Ammonia
Adenosine Triphosphatases
Scanning electron microscopy
Hypoxia
Water
surface area
gills
Cell Count
cells
H-transporting ATP synthase
sodium-potassium-exchanging ATPase
normoxia

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Physiology
  • Biochemistry

Cite this

The ionoregulatory responses to hypoxia in the freshwater rainbow trout oncorhynchus mykiss. / Iftikar, Fathima I.; Matey, Victoria; Wood, Chris M.

In: Physiological and Biochemical Zoology, Vol. 83, No. 2, 01.03.2010, p. 343-355.

Research output: Contribution to journalArticle

Iftikar, Fathima I. ; Matey, Victoria ; Wood, Chris M. / The ionoregulatory responses to hypoxia in the freshwater rainbow trout oncorhynchus mykiss. In: Physiological and Biochemical Zoology. 2010 ; Vol. 83, No. 2. pp. 343-355.
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