Fig. 4. Effects of cadmium (Cd) exposure on total glutathione (GSH) concentrations in gill (A) and hepatopancreas (B) cells of oysters. Cells were incubated for varying periods of time (x-axis) with 0 µmol l^–1 (control) or 2000 µmol l^–1 Cd at 20°C, and their total (reduced + oxidized) GSH levels were determined. P-values for the effect of Cd on GSH levels, as determined by ANOVA, are given. At each exposure time, differences in GSH content between control and Cd-exposed cells were not significant (P>0.05) but the overall effect of Cd estimated by ANOVA was significant in hepatopancreas cells (see P-values in the figures). Vertical bars represent s.e.m. (N=5).