A compartmental model for hepatic transport of taurocholic acid in isolated perfused rat liver.

In order to characterize the transport of bile acids through the liver and to study the influence of drugs on these processes, a kinetic model for hepatobiliary transport of taurocholic acid (TC) using the isolated perfused liver was developed. After the system was brought to a steady state by infusing TC at a constant rate, a tracer dose of 14C-TC was injected into the medium. The medium disappearance of 14C-TC followed a first-order kinetic with a single rate constant. The plot of the biliary secretion rate of radioactivity versus time revealed a curve composed of at least three exponential components. From the described results and the present knowledge of hepatobiliary transport of bile acids we proposed a three compartment model, composed of a perfusion medium compartment and two liver compartments. Parameters calculated from the model constants agreed well with model-independent estimations. The influence of bromosulfophthalein (BSP) on the kinetic parameters was studied to compare the result with the known effect of BSP on hepatic transport of taurocholic acid. BSP decreased the constant describing the fractional transfer of taurocholic acid from medium into the liver, which is in agreement with the inhibition of hepatic uptake of taurocholic acid by BSP. Thus a three compartment model may adequately define the hepatobiliary transport of taurocholic acid in the isolated perfused rat liver.