Two jubilee dates, the 30-year anniversary of Pearse's APUD concept and the 20-year anniversary of the discovery of extrapineal melatonin synthesis in gut are the reason for this commentary.
Thirty years ago, Pearse (1966) first suggested that a specialized and highly organized cell system could exist in which the component cells have as their main feature the capability to produce peptide hormones and biogenic amines. His concept was based on extensive studies on endocrine cells in different organs, including the identification of regulatory substances and a thorough cytochemical and ultrastructural analysis of these cells. He found that so-called 'clear cells' widely dispersed in the organism have a common ability to take up and decarboxylate monoamines to biogenic amines. Thus in 1969 Pearse used the term 'APUD', an acronym for amine precursor uptake and decarboxylation, to designate these cells.
Since identical biogenic amines and regulatory peptides are found both in neurones