Standardization and calibration of whole-body autoradiography for routine semiquantitative analysis of the distribution of ¹⁴C-labeled compounds in animal tissues

Abstract

A procedure is described and evaluated for the standardization and densitometric calibration of whole-body autoradiography (WBAR) using ¹⁴C-labeled compounds. Calibration was achieved using uniform ¹⁴C-labeled poly(methyl)methacrylate standards. The mathematical relationship between activity and autoradiographic image density was linear, resulting in a convenient method for the comparison of relative radioactivity in tissues. Temperature and duration of autoradiographic exposure effected the slope but not the linearity of this relationship. The range of linearity of this function allows for a comparison of radioactivity over two orders of magnitude. The effects of section thickness on autoradiographic density were evaluated and determined to be linear over a range of from 10 to 100 μm. It was concluded that this procedure provides a reliable and reproducible semiquantitative method for the routine evaluation of compound or metabolite distribution and can be a valuable adjunct to pharmacokinetic studies.