RNA was isolated from a normal Fisher rat liver using RNAzol B according to the manufacturer's instructions (Tel-Test, Friendswood, TX). cDNA was synthesized from the purified RNA according to the manufacturer's instructions using the SuperScript III first-strand synthesis system for RT-PCR (Invitrogen). CEACAM1-4S cDNA was amplified by PCR from the total cDNA product using primers: CEACAM1-4S Forward 59CAGGAATT-CATGGAGCTAGCC-TCGGCT-39 and CEACAM1-4S Reverse 59-CGAGTCGACT-CGTCAGAAGGAC CCAGATCC-39. The primers contained EcoRI and SalI restriction sites.