Initial distribution and rate of uptake of sulfobromophthalein in the liver

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Abstract
Multiple indicator-dilution studies of the hepatic uptake of sulfobromophthalein in the dog were carried out using a single intraportal injection of labeled red cells, labeled albumin, and sulfobromophthalein. Analysis of the dilution curves was carried out using a graphical method based upon a flow-limited linear two-compartment mathematical model system in which the rate of sulfobromophthalein removal was assumed proportional to the product of the concentration in and the volume of the extravascular space. This analysis permitted direct estimation of both the volume of the extravascular space initially accessible to sulfobromophthalein and the rate constant for removal. Sulfobromophthalein was found to be distributed into an extravascular space equivalent in volume to that accessible to albumin. Diminution of the rate constant for removal occurred with increasing dosage, indicating saturation. The initial maximal transport capacity and plasma concentration leading to half maximal initial velocity of transport were estimated. The initial maximal transport capacity is much larger than the maximal steady-state capacity for excretion into bile.