The Role of Serum Albumin in the Hepatic Excretion of Iodipamide

The contrast agent for biliary tract visualization, iodipamide, is strongly bound to serum albumin. The relationship between the affinity of the contrast agent for albumin and its preferential uptake and excretion by the liver has been unclear. The role of serum albumin on hepatic uptake and excretion of iodipamide therefore was investigated on the isolated perfused rabbit liver. With the perfusate containing fully reconstituted rabbit plasma protein or 3.5 g/100 ml rabbit albumin alone, the iodipamide excretion is initially extremely slow. It then increases gradually to about 6 µg/gm liver per min by 60 minutes and thereafter remains constant. The half-time of transfer to the bile is about 130 min. Without albumin in the perfusate the initial clearance rate of iodipamide is rapid, with half-time transfer to the bile of about 40 min. Rabbit serum globulins have no effect on iodipamide excretion. Thus, binding of iodipamide to albumin retards the transfer of iodipamide from plasma to the bile, probably due to competition between albumin and the anion binding protein of the liver.