Quantitative Cytochemistry using Directly Applied Radioactive Reagents

Abstract

WHILE radioactive isotopes have found valuable application in many cytochemical studies of metabolic incorporation processes, little use has so far been made of such labels in cytochemical reactions applied directly to the localization of substances in tissue specimens. Some qualitative applications to enzymic cytochemistry, for example, using metals or phosphorus-32 in deposited products, have been reported¹. We have now examined the applicability of tritium-labelled reagents which form covalent bonds at specific sites in tissue components, as a method in quantitative cytochemistry. The advantages of such a method will include, inter alia (cf. ref. 2): (1) an escape from some of the problems of selectively introducing sufficient light-absorption at specific sites, since the label can be carried on many suitable simple reagent molecules; (2) autoradiographic measurement, which is free of certain of the problems of micro-spectrophotometry and is independent of the molecular environment of the target sites; (3) checks and calibrations of micro-spectrophotometric methods for the same components, and the possibility, at least in principle, of absolute determinations.