Cytochemistry in the bioassay of hormones.

For many pathologists, only pedantry can resolve the difference between the terms "histochemistry" and "cytochemistry". Moreover, the better known subject of histochemistry is not distinguished for its quantification. So it may come as some surprise, that the most sensitive bioassays, of polypeptide hormones, that are currently available and that are about one thousand times as sensitive as the equivalent radioimmunoassays, depend on the quantitative cytochemical measurement of the biochemical changes induced by these hormones in their targetcells. Consequently, we will review (i) how this has come about, that is, how cytochemistry has developed as a rigorous form of cellular biochemistry; (ii) how it has led to the formulation of the highly sensitive cytochemical bioassays of polypeptide hormones and of the biological effects of certain types of immunoglobulins; and (iii) how cytochemistry may possibly be applied in clinical pathology to study the biochemical changes induced by disease processes.