CELLULAR-LOCALIZATION AND PHARMACOLOGICAL CHARACTERIZATION OF FUNCTIONING ALPHA-1-ADRENOCEPTORS BY FLUORESCENT LIGAND-BINDING AND IMAGE-ANALYSIS REVEALS IDENTICAL BINDING-PROPERTIES OF CLUSTERED AND DIFFUSE POPULATIONS OF RECEPTORS

A fluorescent quinazoline derivative was shown to retain high affinity for, and act as a competitive antagonist at, alpha-1 adrenoceptors. T his allowed it to be used in live cells to localize receptors and to q uantify receptor binding characteristics. The technique was demonstrat ed and validated on fibrobasts transfected with a recombinant alpha-1 d adrenoceptor. Using confocal la;ser scanning microscopy and image an alysis methods both diffuse and clustered binding sites were found: th eir binding characteristics were assessed and found comparable to radi oligand binding on membrane preparations. This approach should have wi despread applicability in nonradioactive assays determining the locati on, quantity and binding properties of receptors and other biological molecules on live tissue.