Inorganic mercury (Hg2+) and herbicides are important contaminants of world water systems with effects on aquatic organisms and humans. The uptake of Hg2+ and glycine by the gills of the bivalve mollusks Mytilus californianus and Anodonta californiensis was determined. Additionally, the effects of glycine, 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4-dinitrophenol (DNP) on the uptake of Hg2+ were also determined. The loss of primary amines from the excised gills of both species was measured in the presence and absence of Hg2+ or MeHg+. The results indicate that (1) the uptake of Hg2+ is approximately equivalent in both species; (2) comparison of the uptakes with that of inulin, which occupies only extracellular space, shows that Hg2+ is taken up; (3) the uptake of Hg2+ is slightly altered by the presence of glycine and herbicides such as 2,4-D and DNP; (4) the rate of loss of primary amines was highly increased relative to the control by the presence of Hg2+ and to a lesser extent MeHg+ for both species. These results showed that both inorganic and MeHg+ are effective in disrupting the permeability of cell membranes, causing leakage of essential amino acids from the cell. This could result in discharge of potential gradients, reduced efficiency of energy coupling, and consequently cell death. (C) 2008 Elsevier Inc. All rights reserved.