Hepatocytes isolated from F344 rats were transplanted into the liver of congenic albumin-deficient rats (Nagase's analbuminemic rats NAR]) by infusion into the mesenteric vein. Both albumin-positive hepatocytes in the liver and the serum albumin level increased proportionally to the number of the infused F344 hepatocytes in the recipients. However, there was no such increase in the control rats which had received transplantation of NAR hepatocytes. After the polymerase chain reaction (PCR)-mediated analysis of cDNA and genomic DNA of the recipient livers, the implantation of the F344 hepatocytes was confirmed by the increase in normal albumin mRNA and the presence of 7 bp which are missing in the NAR albumin gene. Although treatment of NAR with the 2-acetylaminofluorene diet turned albumin-negative hepatocytes to positive ones, the sequence of the normal albumin gene could not be identified in the NAR liver. This study demonstrates that the hepatocytes infused into the portal vein are readily organized into the host liver parenchyma and continue to produce albumin.