The protective role of dietary calcium against cadmium uptake and toxicity in freshwater fish: An Important role for the stomach

Chris M. Wood, Natasha M. Franklin, Som Niyogi

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

Waterborne cadmium causes toxicity in freshwater fish by inducing hypocalcaemia. Research on the rainbow trout (Oncorhynchus mykiss), a sensitive model species, has demonstrated that this occurs because Cd2+ ions compete with waterborne Ca2+ ions for the active branchial uptake pathway which normally ensures internal homeostasis of calcium levels. Therefore, increases in waterborne calcium concentrations (?hardness') protect against waterborne cadmium uptake and toxicity in both acute and chronic exposures. Increases in dietary calcium concentration also protect against waterborne exposure, because elevated gastrointestinal calcium uptake down-regulates the Ca2+ uptake pathway at the gills, thereby simultaneously reducing Cd2+ entry. Furthermore, dietary calcium also protects against dietborne cadmium exposure, although the physiological mechanisms appear to differ from those at the gills. Surprisingly, the principal site of this inhibitory action of dietary calcium on gastrointestinal cadmium uptake appears to be the stomach, which is also the major site of gastrointestinal calcium uptake, rather than the intestine as in mammals. These results underline the importance of considering not only water chemistry but also dietary chemistry in the environmental regulation of cadmium, and suggest that fish in the wild under chronic cadmium stress would benefit by switching to a more calcium-rich diet. While diet switching has been seen in the wild in fish under metal stress, its etiology remains unknown; to date, laboratory experiments have not been able to show that voluntary diet-switching of an adaptive nature actually occurs.

Original languageEnglish (US)
Pages (from-to)389-394
Number of pages6
JournalEnvironmental Chemistry
Volume3
Issue number6
DOIs
StatePublished - Dec 27 2006

Keywords

  • Aquatic chemistry
  • Cadmium
  • Calcium
  • Fish
  • Hardness
  • Metal uptake

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Chemistry (miscellaneous)
  • Environmental Chemistry

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