Decreased Carbohydrate Content of Rat Plasma Apolipoproteins in Galactosamine Hepatitis

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Abstract
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 [very low density lipoprotein], LDL [low density lipoprotein] and HDL [high density lipoprotein] of control animals, the carbohydrate content was 5.5, 3.4 and 2.9% of dry weight apolipoprotein, respectively. Twenty-four 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, 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, was found.