Radioligand Binding Measurement of Receptor Sequestration in Intact and Permeabilized Cells

A frequently observed adaptive response to chronic agonist occupancy of cell surface receptors is a process in which receptors become internalized or sequestered into a cell compartment to which hydrophilic ligands have only a limited access (1 –3 ). Although receptor sequestration has frequently been documented, its physiological significance and underlying mechanism(s) remain obscure. This is largely the result of the routine use of intact cells for the measurement of sequestration events.