[Biogenic amines in endocrine cells producing polypeptide hormones. The APUD-cells (Pearse) (author's transl)].

APUD-cells (A = Amine, P = Pprecursor, U = Uptake, D = Decarboxylation) are endocrine cells with numerous common characteristics: 1. They produce polypeptide hormones of low molecular weight. 2. They possess specific 1-amino acid decarboxylases to synthesize catecholamines and/or 5-hydroxytryptamine from precursors. 3. A part of the APUD-cell family primarily accumulates biogenic amines within their cytoplasm. 4. All APUD-cells are rich in specific secretory granules that are the morphological substrate for most of their common features.--Enzyme histochemically the APUD-cells represent a rather heterogenous population. The capacity to take up biogenic amines from the blood is confined to a smaller numer of APUD-cells. The concept of the APUD-cells representing a peripheral neurosecretory system (Pearse und Polak, 1971) appears to be premature. It is probable that in several APUD-cells the accumulation of biogenic amines only constitutes a phenomenon without any physiological relevance which, notwithstanding, could explain pathological reactions of APUD-cells.