In vitro evidence for the ionoregulatory role of rainbow trout mucus in acid, acid/aluminium and zinc toxicity

Rainbow trout body mucus dialysed with acidified distilled water at pH 7,5 and 3 experienced ion depletion which was greatest at pH 3 and minimal between pH 7 and 5. Mucus Na+ loss is exacerbated in the presence of 1 mg I−1 aluminium as A12(SO4), at pH 5 and 7. Al2(SO4), causes greater depletion of Na+ from mucus than A1C13. A lethal level of zinc (2 mg 1−1) does not deplete mucus Na− or K+, unlike a lethal level of aluminium (1 mg 1−1) at pH 7. The results are discussed in terms of the ionoregulatory role of mucus in heavy metal and acid toxicity.