INFLUENCE OF MONOSACCHARIDE DERIVATIVES ON LIVER-CELL GLYCOSAMINOGLYCAN SYNTHESIS - 3-DEOXY-D-XYLO-HEXOSE (3-DEOXY-D-GALACTOSE) AND METHYL (METHYL 4-CHLORO-4-DEOXY-BETA-D-GALACTOPYRANOSID) URONATE

An improved, convenient synthesis of 3-deoxy-D-xylo-hexose (3-deoxy-D- galactose) has been developed, and the chemical synthesis of a novel m onosaccharide derivative, methyl (methyl 4-chloro-3-deoxy-beta-D-galac topyranosid)uronate (compound 10), is described. Using primary hepatoc ytes in culture, each was used to explore its effect on glycosaminogly can (GAG) synthesis. In the absence of analogues hepatocytes synthesiz e primarily (92-95%) heparan sulphate. At 1 mM, 3-deoxy-D-galactose ha d little observable effect on either liver cell GAG or protein synthes is. At 10 mM and 20 mM, 3-deoxy-D-galactose reduced [H-3]glucosamine a nd (SO4)-S-35 incorporation into hepatocyte cellular GAGs to, respecti vely, 75% and 60% of the control cells. This inhibition of GAG synthes is occurred without any effect on hepatocyte protein synthesis, indica ting that 3-deoxy-D-galactose's effect on GAG synthesis is not mediate d through an inhibition of proteoglycan core protein synthesis. Furthe rmore, GAGs in the presence of 20 mM of the analogue were significantl y reduced in size, 17 kDa vs. 66 kDa in untreated cells. These results reflect either impaired cellular GAG chain elongation, and/or altered GAG chain degradation. Compound 10 exhibited a concentration-dependen t inhibition of both hepatocyte cellular GAG and protein synthesis. At concentrations of 5, 10 and 20 mM, compound 10 inhibited GAG and prot ein synthesis by 20, 65 and 90%, respectively. Exogenous uridine was a ble to restore partially the inhibition of protein synthesis, but was unable to reverse the effect of compound 10 on GAG synthesis. These re sults show that part of the effect of compound 10 on GAG synthesis is not mediated by an inhibition of proteoglycan core protein synthesis. GAGs in the presence of compound 10 are half as large as those in the absence of this compound (33 and 66 kDa, respectively). These results again may reflect either impaired cellular GAG chain elongation and/or altered GAG chain degradation. Potential metabolic routes for each an alogue's effect are presented.