Dynamic determination of kinetic parameters for the interaction between polypeptide hormones and cell-surface receptors in the perfused rat liver by the multiple-indicator dilution method.

Publisher Website
Google Scholar
Abstract
Hepatic elimination of epidermal growth factor (EGF) via receptor-mediated endocytosis was studied by a multiple-indicator dilution method in the isolated perfused rat liver, in which cell polarity and spatial organization are maintained. In this method EGF was given with inulin, and extracellular reference, as a bolus into the portal vein, and dilution curves of both compounds in the hepatic vein effluent were analyzed. Analysis of the dilution curve for EGF, compared wtih that for somatostatin, which showed no specific binding to isolated live plasma membranes, resulted as follows: (i) both extraction ratio and distribution volume of 125I-labeled EGF decreased as the injected amount of unlabeled EGF increased; (ii) the ratio plot [In (inulin/EGF) versus time] of the dilution curve for EGF exhibited an upward straight line initially for a short period of time (.apprxeq. 10 sec), whereas the ratio plot [In (inulin/somatostatin) versus time] of somatostatin gradually decreased. The multiple-indicator dilution method was used for the other peptides also. Insulin and glucagon, known to have hepatocyte receptors, behaved similarly to EGF in shape of their ratio plots. Thus, analysis of dilution curves can reveal whether or not the cell surface has receptors for certain peptides. In addition, the dilution curves for EGF at various doses (tracer .apprxeq. 30 .mu.g) were analyzed simultaneously based on a kinetic model incorporating the perfusion rate, the association rate constant of EGF to surface receptors (kon), the dissociation rate constant of EGF from the EGF-receptor complex (koff), and the sequestration rate constant of the complex. The kinetic parameters [the dissociation constant (Kd = koff/kon) and the number of surface receptors] calculated by this analysis were comparable with reported values obtained by using liver homogenates. We conclude that the multiple-indicator dilution method is a good tool for analyzing the dynamics of peptide hormones.sbd.cell-surface receptor interaction under a condition in which spatial architecture of the liver is maintained.

This publication has 22 references indexed in Scilit: