Impaired immune function has long been documented in patients with obstructive jaundice, and those with jaundice due to extrahepatic biliary obstruction still experience a high rate of postoperative complications and death. Transforming growth factor-beta1 (TGFbeta1) appears to be an important regulator of both normal and pathologic conditions in the liver. Monocyte chemoattractant protein-1 (MCP-1) is an important mediator of monocyte recruitment to inflammatory sites. We hypothesize that obstructive jaundice may alter serum TGFbeta1 and MCP-1 expressions in the rat and that oral bile acid or glutamine (or both) can restore the altered serum TGFbeta1 and MCP-1 expression in rats with obstructive jaundice. Male Sprague-Dawley rats weighing 250 to 300 g were randomized to four groups (n = 10 in each group). Group 1 underwent a sham operation with oral normal saline administration. Group 2 underwent common bile duct ligation (CBDL) with oral normal saline administration. Group 3 underwent CBDL with oral bile acid replacement. Group 4 underwent CBDL with oral glutamine administration. Animals were sacrificed after 3 days (n = 5) and 7 days (n = 5), and blood samples were collected. Serum was obtained after centrifugation for measurement of TGFbeta1 and MCP-1 levels by an enzyme-linked immunosorbent assay. The serum TGFbeta1 level was significantly elevated (p = 0.006) 3 days after CBDL. Oral glutamine administration prevented this elevation, but oral bile acid replacement did not. The serum MCP-1 level showed similar changes. After 3 days of obstructive jaundice, the TGFbeta1 and MCP-1 levels were altered in the rat. Oral glutamine administration, not oral bile acid replacement, was able to prevent these alterations.