CO4-MMP serum levels in carbon tetrachloride-treated rats. (A) Serum 1438'GTPSVDHGFL'1447 (CO4-MMP) was assessed in control rats at death (controls) as well as in carbon tetrachloride (CCl4)-treated rats at death at weeks 8, 12, 16 and 20. The results shown are means ± SEM. (B) Serum CO4-MMP in all controls pooled and CCl4 rats stratified into quartiles according to total collagen in the liver. (C) Correlations between CO4-MMP and Sirius red in (C) CCl4 rats and (D) control rats. Asterisks indicate statistical significance as indicated by bars (**P < 0.05, ***P < 0.001, ns = nonsignificant difference).