Measurement of specific radioactivities in labelled hormones by self-displacement analysis

Abstract

A graphical method is described that allows the determination of specific radioactivities of radioactively labeled hormones [in rats]. This method combines the self-displacement technique, plotting bound/free ratios vs. mass of unlabeled hormone or total radioactivity of labeled preparation added to the receptor preparation, and the maximal binding capacity of the labeled hormone. The procedure presented herein provides a more realistic specific radioactivity for use in all binding experiments. Application of the method is demonstrated for 125I-labeled ovine prolactin, and data are presented for 125I-labeled human choriogonadotropin and [3H]testosterone.