Incorporation of non-acetylated hexosamines into plasma membrane glycoproteins of liver cells after galactosamine injection

The following procedure for the detection of non-acetylated amino sugars in the plasma membrane was established: i) derivatization of free amino groups with dansyl-chloride, ii) hydrolysis with 3 M HCl (for 4 h at 105 degrees C) to liberate the dansylated carbohydrate moieties from the plasma membrane, iii) purification of the dansylated amino sugars by paper chromatography and subsequent analysis by thin-layer chromatography. Using this procedure, plasma membranes from rat liver were analysed after injection of D-14C]galactosamine. For this purpose, rats were divided into three groups: the first received D-galactosamine.HCl at a dose of 2 mg/kg b.w., the second at a dose of 75 mg/kg b.w. and the third at a hepatitis-inducing dose of 260 mg/kg b.w.. In all three groups the majority of the protein-bound radioactivity in the plasma membrane was not dansylated, thus representing N-acetylated amino sugars. At a dose of 2 mg/kg, only 0.34% of the protein-bound radioactivity in the plasma membrane reacted with dansyl-chloride. At a dose of 70 mg/kg this value increased to 1.9%. At 260 mg/kg the value was 3.6%. These results indicate that the incorporation of non-acetylated amino sugar into the plasma membrane was dose-dependent and reached 90 pmol per mg plasma membrane protein during galactosamine injury. However, this incorporation of non-acetylated amino sugars into the plasma membrane did not represent a pathological mechanism responsible for the onset of the galactosamine-induced liver injury.(ABSTRACT TRUNCATED AT 250 WORDS)