N-acetylglucosaminyltransferases 111 and V (GnT-III and -V) are key enzymes in the synthesis of the branches of asparagine-linked oligosaccharides. Although their messenger RNAs (mRNAs) are expressed in various rat tissues, they are not detected in normal rat liver. Expression of the GnT-111 and -V mRNAs, however, increased in regenerating liver after two-thirds partial hepatectomy compared with sham-operated rats. The enzymatic activities of GnT-I11 and -V increased in proportion to mRNA expression. To determine which type of cells in the liver have high activities of these glycosyltransferases, hepatocytes and nonparenchymal cells were separated by means of a two-step collagenase perfusion technique. GnT-111 activity was only detected in nonparenchymal cells of normal rat liver. However, during liver regeneration, GnT-111 activity increased and thus was also detectable in hepatocytes. GnT-V activity was detected in both types of cells. These data were sup- ported by reverse transcription-polymerase chain reaction results. Although the mechanism underlying the induction of these glycosyltransferases is unknown, lectin blot analysis showed that oligosaccharides in many glycoproteins, including hepatocyte growth factor, a major growth factor associated with liver regeneration, were newly synthesized during liver regeneration. This is the first report on the expression of glycosyltransferases during liver regeneration and suggests that there are different mechanisms involved in regulation of the genes of GnT-111 and -V during liver regeneration. (HEPA-