Administration of D-galactosamine (GalNH2) is known to produce alterations in plasma glycoprotein levels, including alpha 1-antitrypsin. The authors have studied the effects of GalNH2 on circulating protein bound carbohydrates and on the plasma concentrations of two alpha 1-antiproteases, transferrin, IgG, and albumin in rats. The alpha 1-antiproteases from GalNH2-treated rats were isolated and their molecular weight, isoelectric point, and carbohydrate composition compared with those of control rat alpha 1-antiproteases. Total plasma protein, albumin, and transferrin levels in the GalNH2-treated rats do not differ significantly from those of control rats. Plasma protein-bound carbohydrate is decreased significantly in the experimental animals, compared with controls: sialic acid decreased 60%, neutral sugars decreased 43%, and amino sugars decreased 38%. The concentrations of alpha 1-antitrypsin (AAT) and a higher molecular weight alpha 1-antiprotease designated AP2 are decreased by 79% and 38%, respectively. AAT isolated from the plasma of GalNH2-treated rats contains 2-3 fewer moles of sialic acid, 3 fewer moles of neutral sugar, and 2 fewer moles of amino sugar per mole of antiprotease than AAT isolated from controls. AP2 from GalNH2-treated rats contains 1 fewer mole each of sialic acid, neutral sugar, and amino sugar per mole of antiprotease than AP2 from controls. These alterations are similar to those seen in humans with genetically determined alpha 1-antiprotease deficiency.
Animals Blood Proteins