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

Abstract

The incorporation of glycine-2-C14 into plasma haptoglobin, fibrinogen, and gamma-globulin is studied in 2 hepatectomized and 4 intact dogs during response to in-flammation. There is incorporation of radioactivity into gamma-glo-Dulin but not into haptoglobin in the hepatectomized animals. The specific activity of haptoglobin isolated from hepatic vein plasma is higher than that isolated from simultaneously obtained portal vein plasma at all times up to one hour in the 4 intact dogs. This difference in specific activity is also observed in the case of fibrinogen. There is no difference in specific activity between gamma-globulin isolated from portal vein plasma and that obtained simultaneously from hepatic vein plasma. Labeled haptoglobin and fibrinogen appear in thoracic duct lymph only after approximately 35 minutes, and specific activities are considerably lower than corresponding specific activities in the plasma throughout the period of study. In contrast, labeled gamma-globulin appears in the lymph within 10 minutes, and specific activities are comparable to those in the plasma. These results provide evidence that haptoglobin is synthesized by the canine liver. They also indicate that newly synthesized haptoglobin and fibrinogen molecules enter the plasma directly, whereas gamma-globulin is at least partially released directly into the lymph.