Decreased carbohydrate content of rat plasma apolipoproteins in galactosamine hepatitis

The total carbohydrate content and the monosaccharide composition of plasma apolipoproteins isolated from normal and D-galactosamine-treated rats were investigated. In the lipoprotein classes VLDL, LDL and HDL of control animals, the carbohydrate content was 5,5%, 3,4% and 2,9% of dry weight apolipoprotein, respectively. 24 h after galactosamine treatment, these values dropped to 1.8%, 1.6% and 2.3%. The reduction of the carbohydrate content in VLDL and LDL was mainly due to a decrease of the following monosaccharides: Mannose, galactose, N-acetylglucosamine and sialic acid. Minor changes were observed in the fucose, glucose and N-acetylgalactosamine content. Particularly, the mannose/galactose ratio in the LDL fraction fell from 2.3 in control animals to 1.0 in the galactosamine-treated animals. In another series of experiments, the time course of these carbohydrate alterations in the LDL apolipoprotein was studied. As early as 3 h after galactosamine application, we found a reduction of the mannose, galactose and N-acetylglucosamine levels, with the absolute minimum at 24 h, and later on a normalization at 48 and 72 h.