1 - The APUD concept and hormone production

Abstract

In 1968 the acron ym APUD was attached to a series of cells. widely distributed all over the body , which appeared to possess a significant number of common cytochemical and ultrastructural properties. These properties had already been described (Pearse, 1966a and b), and attached to a small original series (Adrenomedullary chromaffin, Enterochromaftin , Corticotroph, Melanotroph , Islet beta , Thyroid C and Mast cells). Despite their amine-handling characteristics. which were expressed by the acron ym APUD (Amine Precursor Uptake and Decarboxylation), the primary function of a significant proportion of the cells appeared to be the production not of one or other of the biogenic amines but of low molecular weight polypeptides. These were, in some cases , known peptide hormones. The association of peptide hormone production with the potential or actual conversion of one or other of the two precursor amino acids (5hydroxytryptophan, L 3,4-dihydroxyphenylalanine) to the corresponding amine was considered to indicate a 'neural' origin for the cells possessing these characteristics (Pearse 1966a). The first 'official' (1968) list of APUD cells is given in Table 1. Attributions and nomenclature are presented in the original 1968 terms where 'supposed' was used to draw attention to the predominant , but not necessarily correct, view held at that time. The principal casualty from the 1968 list was the mast cell. removed because of its non-compliance with a more or less obligatory list of properties. It will be noted that , with the exception of the two cells derived from Rathke's pouch, all the APUD cells were presumed, at that time, to originate from endodermal precursors. This must not be understood to be the same thing as precursors present in the endoderm. The diffuse distribution of the eight cell types, and their predominant localization in the gut and its derivatives was noted as significant. With regard to the origin of the cells, it had been suggested from the beginning (Pearse, 1966a) that the amine storage mechanism, and the