The synthesis of a-fetoprotein and other fetal plasma proteins was studied by perfusion of isolated human fetal livers with an artificial medium containing leu-
The incorporation of I e~c i n e -l -~~C into serum proteins was determined by autoradiography after electrophoresis on cellulose acetate, immunoelectrophoresis, or immunodiffusion. Radioactivity was found in a-fetoprotein, albumin, a,-antitrypsin,Gc-protein and a-lipoprotein -indicating hepatic synthesis of these proteins. No radioactivity was found in IgG present in the perfusion medium, and no haptoglobin was found in the medium.In 1956, Bergstrand and Czar detected a plasma protein which was unique to the fetus and absent in adult man. This protein migrated between albumin and a-globulin on paper electrophoresis, and was therefore called a-fetoprotein. An immunologically and electrophoretically identical protein was discovered in the serum of patients with hepatocellular cancer by Tatarinov in 1965. Recently, the amino acid, neutral carbohydrate and polypeptide composition of both these proteins have been determined (Nishi, 1970;Ruoslahti and Seppala, 1971;Ruoslahti et al., 1971). The tumor and fetal proteins are indistinguishable by these methods.In order to quantify the rate of synthesis and release of a-fetoprotein by the human fetal liver, a new technique was developed for the perfusion of the isolated organ. De novo synthesis in this experimental model was studied by measuring the incorporation of radioactivity into a number of specific proteins after the addition of leucine-I4C into the perfusion medium.
MATERIAL AND METHODS
MaterialThree fetuses were obtained from therapeutic abortions at the Department of Obstetrics and Gynecology, University Central Hospital, Helsinki. All the pregnancies had proceeded without known medical complications, and were terminated on psychiatric grounds. The gestational ages of the fetuses were 14, 17 and 20 weeks, as determined by obstetric history and crown-rump
