A linear method for determining liver sinusoidal and extravascular volumes.

Abstract

Multiple indicator dilution studies of the hepatic circulation in the dog were carried out using labeled red cells, albumin, inulin, sucrose, sodium, urea, water, and T-1824. The materials were completely recovered in the outflow. Concentrations were expressed as fractions of the injected mass. The outflow pattern of each of the substances was displaced relative to the red cell curve, showing a lower peak concentration and longer transit time. The displacement was largest for water and urea, least for albumin and T-1824, intermediate for inulin, sucrose, and sodium. The results were analyzed using a flow-limited linear two-compartment model system. The analysis yielded estimates of sinusoidal blood volume and of the extravascular volumes of distribution of the diffusible labels. Water and urea volumes agreed with the liver weights and this agreement was taken as validation of the method of analysis. Volumes calculated for the other presumably extracellular substances demonstrated that the rapidly available extracellular space diminishes with increase in the molecular weight of the substance.