Fig. 5. Rates of sodium uptake (nmol g^-1 h^-1) as a function of ambient sodium concentration in the presence of different ambient copper concentrations in juvenile rainbow trout during a 2 h incubation period. The lines are Michaelis—Menten curves (SigmaPlot 4.0 for Windows), and the inset summarizes the derived sodium uptake kinetic parameters J_max (nmol g^-1 h^-1) and K_m (µmol l^-1). Values are means ± S.E.M., N=8 in all cases. In the inset, an asterisk indicates a significant difference from the control condition (18 nmol l^-1 copper).