RECEPTOR LOCALIZATION OF STEROID-HORMONES AND DRUGS - DISCOVERIES THROUGH THE USE OF THAW-MOUNT AND DRY-MOUNT AUTORADIOGRAPHY

The history of receptor autoradiography, its development and applicati ons, testify to the utility of this histochemical technique for locali zing radiolabeled hormones and drugs at cellular and subcellular sites of action in intact tissues. Localization of diffusible compounds has been a challenge that was met through the introduction of the ''thaw- mount'' and ''dry-mount'' autoradiographic techniques thirty years ago . With this cellular receptor autoradiography, used alone or combined with other histochemical techniques, sites of specific binding and dep osition in vivo and in vitro have been characterized. Numerous discove ries, some reviewed in this article, provided information that led to new concepts and opened new areas of research. As an example, in recen t years more than fifty target tissues for vitamin D have been specifi ed, challenging the conventional view about the main biological role o f vitamin D. The functions of most of these vitamin D target tissues a re unrelated to the regulation of systemic calcium homeostasis, but pe rtain to the (seasonal) regulation of endo-and exocrine secretion, cel l proliferation, reproduction, neural, immune and cardiovascular respo nses, and adaptation to stress. Receptor autoradiography with cellular resolution has become an indispensable tool in drug research and deve lopment, since information can be obtained that is difficult or imposs ible to gain otherwise.