AVAILABLE INTRACELLULAR ZN AS A POTENTIAL INDICATOR OF HEAVY-METAL EXPOSURE IN RAINBOW-TROUT HEPATOCYTES

The measurement of available Zn in rainbow trout hepatocytes exposed t o a selection of heavy metals was evaluated as a potential end point f or assessing heavy metal exposure. Induction of metallothionein, a wel l-known biomarker for heavy metal exposure, was also evaluated concurr ently with available Zn measurements. Rainbow trout hepatocytes were e xposed to several concentrations of copper, cadmium, mercury, silver, arsenite, and zinc salts for 48 h at 15 degrees C. Hepatocytes were al so exposed to industrial effluent from a metallurgy plant. After the e xposure period, hepatocytes were analyzed for metallothionein (MT) and available Zn levels. The results showed that, with divalent metals, a vailable Zn increased with MT levels; there was a significant correlat ion (R = 0,600; p = 0.0006) between the two. Moreover, the industrial effluent proved to be an inducer of available Zn in hepatocytes, as we ll as of MT. However, cells exposed to Ag responded with higher levels of available Zn before showing a corresponding MT induction in cells. Inversely, exposure to arsenite led to increased MT without any chang e in available Zn levels. The value for available Zn tended to be some what overestimated in the presence of metals such as Hg, and to a less er extent Cd. The evaluation of available Zn, in addition to MT, appea rs to be a valid way of assessing exposure to mono- and divalent metal s, though with arsenite, the MT induction response was higher than tha t of available Zn. The specificity of the available Zn biomarker for h eavy metal exposure should be investigated more thoroughly for compari son with the MT biomarker. The measurement of available Zn holds promi se as a new biomarker of heavy metal exposure. (C) 1996 by John Wiley & Sons, Inc.