Quantitative autoradiography of transmitter binding sites with an image analyzer

A computerized image processing system for quantitative receptor autoradiography on tritium-sensitive film is described. The method implements an image analyzer (IBAS 1 + 2) for the acquisition of an image which is evaluated with respect to the regional distribution of binding site densities by a small computer which is connected to a digitizer. Several methodological problems must be considered when using tritium-labelled compounds and an image analyzer. The use of tissue standards and shading procedures, the improvement of signal-to-noise ratio, the calibration of the system which establishes the non-linear relation between grey values and concentration of radioactivity, the contrast enhancement and the quenching problem are discussed. This method permits a quick and precise quantitative analysis of binding site distribution in receptor autoradiography.