SEROLOGIC ASSAY FOR SECRETORY COMPONENT DISTINGUISHES MECHANICAL FROMHEPATOCELLULAR CHOLESTASIS IN HUMANS

In rats, serum secretory component (SC) is elevated in mechanical but not hepatocellular cholestasis. To determine if serum SC might disting uish cholestatic syndromes in humans, serum samples were obtained from control subjects and patients with mechanical and hepatocellular chol estasis. Equal volumes of serum were assayed for SC by immunoblotting with an antibody specific for human SC. Quantitative densitometry of t hese immunoblots showed that in mechanically obstructed patients serum SC was reversibly elevated to a level similar to 10-fold higher than that of patients with hepatocellular cholestasis (P < 0.001). When com paring the two cholestatic groups, levels of serum alkaline phosphatas e, but not bilirubin and alanine aminotransferase, were significantly higher in the group with mechanical cholestasis (P < 0.01). When compa ring individual patients, serum SC was more reliable than alkaline pho sphatase in distinguishing the two cholestatic syndromes (P < 0.05). T hus, serum SC may distinguish mechanical from hepatocellular cholestas is in humans.