Relative Cp activity as a function of liver and serum copper levels. Plots depict the relationship between serum (A) and liver (B) copper and Cp activity. Lines or curves fitting the data were derived by linear regression for Cp activity versus serum copper and by nonlinear regression for Cp activity versus liver copper. Data for liver copper were log transformed for reasons addressed under “Statistical analysis”; actual values for liver copper (in micrograms per gram dry weight) are shown below indicates the y-axis in parentheses. In panel A, P < .0001. r indicates Pearson correlation coefficient.