Fig. 4. (A) Overall copper (64Cu) uptake rates (pmol g-1
h-1) in the presence of different ambient sodium concentrations
(indicated by different symbols), (B) calculated `sodium-insensitive' copper
uptake rates (pmol g-1 h-1) and (C) `sodium-sensitive'
copper uptake rates (pmol g-1 h-1) as a function of
ambient copper concentration in juvenile rainbow trout during a 2 h incubation
period. The `sodium-insensitive' copper uptake rates were determined
mathematically as the Jmin (see text) in a hyperbolic
curve fit (SigmaPlot 4.0 for Windows) to copper uptake rates as a function of
ambient sodium concentration. `Sodium-sensitive' copper uptake rates were
determined as the difference between the overall copper uptake and the
`sodium-insensitive' copper uptake. Inset: example of a hyperbolic curve fit:
copper uptake during a 2 h incubation at 145 nmol l-1 copper as a
function of ambient sodium concentration. Values are means ± S.E.M.,
N=8 in all cases.