Synthesis in vitro of glycoprotein in regenerating rat liver.
The metabolism of glucosamine in regenerating rat liver was studied in liver slices. [1-14C] Glucosamine was incorporated into acid-soluble fraction, rapidly converted to UDP-N-acetylhexosamine and transferred to acid-insoluble fraction. Electrophoretic analysis revealed that most of the radioactive macromolecules released from the slices to the incubation medium were plasma glycoproteins. The incorporation of [1-14C] glucosamine into UDP-N-acetylhexosamine significantly increased from 6 h to 48 h after partial hepatectomy. On the contrary, the incorporation into acid-insoluble fractions of slice and medium decreased to about 50% of the control values. The rate of transfer of N-acetylhexosamine from UDP-N-acetylhexosamine to acid-soluble fractions also decreased at 12 h and 48 h respectively. This indicates that the transfer of N-acetylhexosamine to glycoproteins decreases during 48 h of liver regeneration. The enhancement of [1-14C] glucosamine incorporation into UDP-N-acetylhexosamine is due to an accumulation of the label in the larger pool of this compound. Evidently, some control mechanism may operate on the transfer of N-acetylhexosamine to glycoproteins in regenerating rat liver.