Fig. 4. Caspase-3 activity in freshly isolated oyster hemocytes (Fresh) and hemocytes incubated for 72 h with vehicle, 50 or 200 µmol l^-1 of cadmium. Cyt c: activation of caspase-3 from vehicle-treated hemocytes with cytochrome c and dATP. Apoptotic thymocytes: caspase-3 activity in growth-factor-deprived murine thymocytes used as a positive control. Vertical bars represent S.E.M. Values that are not significantly different from each other are denoted by the same letters (P<0.05; N=5-6).