By P. Part, O. Svanberg, A. Kiessling
Water Research, Volume 19, Issue 4, 1985, Pages 427-434, ISSN 0043-1354, DOI: 10.1016/0043-1354(85)90033-8.

The uptake of cadmium in perfused gills from rainbow trout (Salmo gairdneri, Rich.) in different water qualities has been studied.
In the naturally hard alkaline Uppsala tap water, the calcium concentration was the dominating factor controlling the cadmium transfer through the gills. A strong inverse relationship was measured between the external Ca2+ concentration up to 3 mmol l-1 (< 120 mg Ca2+ l-1), and the Cd transfer. A higher Ca2+ concentration (10 mmol l-1) did not further affect the transfer. Magnesium decreased the transfer, but only at concentrations 4 to 5 times as high as calcium. At a constant Ca2+/Mg2+ hardness, the transfer was a function of the free cadmium ion activity (Cd2+). Ca2+ and Mg2+ selectively reduced the transfer by a biological mechanism, probably by changing the permeability of the gill epithelium.
Cd transfer was not dependent on pH in the range pH 5-7. A lower transfer at pH 7.6 was related to a lower Cd2+ activity, probably due to the formation of non-available bicarbonate/carbonate complexes.
Cd transfer decreased in the presence of 121 mmol l-1 NaCl (0.7% salinity). This decrease was not caused by the altered osmotic gradient over the gills. The transfer was proportional to the Cd2+ activity. CdCl+ and CdCl2 were not available for the gills.
The retention of Cd in perfused gill tissue was proportional to the Cd2+ activity in all water qualities tested. Tissue accumulation of Cd was not sensitive to external Ca and Mg and in this respect different from the transfer.
Keywords: Cd uptake; fish gills; gill perfusion; hardness; alkalinity; salinity; pH; osmolarity; Salmo gairdneri

More details...