The use of the isolated perfused liver to detect alterations to plasma proteins

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Abstract
The behavior of serum albumin and [gamma] -globulin labeled with I131 was investigated in the isolated perfused rat liver. Such a liver was capable of preferentially removing and then breaking down very small proportions of altered protein molecules present in preparations of plasma proteins isolated by the usual methods. The proportions of such altered molecules actually present varied widely according, at least in part, to the methods used for the preparation of each protein. Very rapid breakdown occurred when human albumin was presented to the liver as part of an antigen-antibody complex. On the other hand, very slow liberation of I131 was found if the (I131) proteins were first injected into rats and then, 48 hours later, the plasma of these animals was used as the dose material for the liver perfusions. No difference could be detected between the behavior of rat and human albumins which had been thus pretreated. The observed rate of catabolism of rat albumin if pretreated as above was very low. This suggests that in the rat the liver is responsible for not more than about 10% of the total breakdown of serum albumin which occurs in vivo. The proportions of these proteins which were retained in the liver after 5 hours perfusion and after finally perfusing out with saline were measured.