Haptoglobin Synthesis. I. In Vivo Studies of the Production of Haptoglobin, Fibrinogen, and γ-Globulin by the Canine Liver*

Haptoglobin is an a2 plasma glycoprotein that forms a stable complex with hemoglobin (1-5). The complex is cleared from the plasma much more rapidly than free haptoglobin so that marked hypoor anhaptoglobinemia is a concomitant of hemolysis (6, 7). Since free hemoglobin passes readily into the urine, whereas the complex, perhaps owing to its much greater size, does not, haptoglobin may play a role in the conservation of iron by the body (5, 7). Haptoglobin concentration increases markedly in man (8-12) and animals (13-15) in the presence of inflammation or tissue necrosis. Estrogen administration depresses the haptoglobin concentration in the serum of man (10). The site of synthesis of this protein is unknown although the liver has been suggested (16), for it is known that in some instances of parenchymatous liver disease haptoglobin concentration is reduced (10, 17). At least theoretically this might be the result of decreased synthesis by a damaged organ. However, increased hemoglobin