GENE-EXPRESSION OF N-ACETYLGLUCOSAMINYLTRANSFERASE-III AND N-ACETYLGLUCOSAMINYLTRANSFERASE-V - A POSSIBLE IMPLICATION FOR LIVER-REGENERATION

N-acetylglucosaminyltransferases In: and V (GnT-III and -V) are key en zymes in the synthesis of the branches of asparagine-linked oligosacch arides. Although their messenger RNAs (mRNAs) are expressed in various rat tissues, they are not detected in normal rat liver. Expression of the GnT-III and -V mRNAs, however, increased in regenerating liver af ter two-thirds partial hepatectomy compared with sham-operated rats. T he enzymatic activities of GnT-III and -V increased in proportion to m RNA expression, To determine which type of cells in the liver have hig h activities of these glycosyltransferases, hepatocytes and nonparench ymal cells were separated by means of a two-step collagenase perfusion technique, GnT-III activity was only detected in nonparenchymal cells of normal rat liver, However, during liver regeneration, GnT-III acti vity increased and thus was also detectable in hepatocytes. GnT-V acti vity was detected in both types of cells, These data were supported by reverse transcription-polymerase chain reaction results. Although the mechanism underlying the induction of these glycosyltransferases is u nknown, lectin blot analysis showed that oligosaccharides in many glyc oproteins, including hepatocyte growth factor, a major growth factor a ssociated with liver regeneration, were newly synthesized during liver regeneration, This is the first report on the expression of glycosylt ransferases during Liver regeneration and suggests that there are diff erent mechanisms involved in regulation of the genes of GnT-III and -V during Liver regeneration.