EFFECT OF SELENIUM ON THE UPTAKE OF METHYL MERCURY ACROSS PERFUSED GILLS OF RAINBOW-TROUT ONCORHYNCHUS-MYKISS

The uptake of methyl mercury was measured across the perfused gills of rainbow trout Oncorhynchus mykiss. The effect of selenium, either in the blood (perfusion medium), or in the water was investigated. Methyl mercury was effectively taken up from the water across the gills into the perfusate. The uptake rate reached a stable level after 30 min pe rfusion. When the gills were placed in mercury free water after exposu re to mercury in the water for 1 h, they continued to liberate signifi cant amounts of accumulated mercury into the perfusate. Exposure to se lenite (SeIV) or selenate (VI) (0.075-0.75 mu M) in the external mediu m did not affect the uptake of methyl mercury across the gills or the liberation of the metal from the gills. Internal selenite or selenate (7.5 mu M) augmented the uptake of methyl mercury across the gills and internal selenite also increased the amounts of liberated methyl merc ury from the gills in the unload period, Internal selenium, increased the mercury accumulation in the gills, whereas, external selenium did nor alter the mercury accumulation in the gills. Uptake of selenium fr om the water across the gills occurred very slowly. (C) 1998 Published by Elsevier Science B.V. All rights reserved.