Model Studies with Dual Labelling

Abstract

The purpose of this study is to discuss the possible applications of a model involving dual isotope-studies of a ligand and in particular of Fluorescein. Selective accumulation of a radioactive substance within an organ is the main property upon which scintigraphic imaging is based. The possibility of a preferential localization may be the result of direct introduction of the isotope into the blood-stream supplying the organ or due to affinity of the ligand for a particular tissue. It is well known that there are six main biological mechanisms which are responsible for the localization of radiopharmaceuticals in various organs or physiological compartments. These are phagocytosis, cell sequestration, capillary blockade, simple or exchange diffusion, compartmental localization and active transport. Because our model is based upon the use of phosphorus-32 which localizes in tumours by active transport this biological mechanism has been specifically examined.