QUANTITATIVE RECEPTOR AUTORADIOGRAPHY WITH TRITIUM-LABELED LIGANDS - COMPARISON OF BIOCHEMICAL AND DENSITOMETRIC MEASUREMENTS

Tritium-labeled receptor ligands are commonly used for quantitative receptor autoradiography with LKB Ultrofilm. Estimates of tritium concentrations by optical density measurements were compared with direct measurements of tritium concentrations by scintillation counting. Predominantly grey matter regions of rat brain showed similar tritium concentrations when measured by either method. Optical density reading of white matter regions indicated a lower tritium concentration than determined by direct measurement with scintillation counting. Measurements of receptor density by quantitative autoradiography were compared with radioligand-binding measurements on microdissected brain regions. Higher per mg protein levels of muscarinic receptors were obtained by quantitative autoradiography, comparable to the specific activity of receptors found in purified membranes.