Phylogenetic aspects of pancreastatin- and chromogranin-like immunoreactive cells in the gastro-entero-pancreatic neuroendocrine system of vertebrates.

Using a battery of region-specific antisera raised against different amino acid sequences of pancreastatin (Pst) (Pst-1-6, Pst-1-17, Pst-14-49, Pst-33-49) as well as two antisera raised against chromogranin (Cg) A and CgA/B and the biotin-avidin technique, the phylogenetic distribution of Pst-immunoreactive (-IR) and Cg-IR cells was studied in the gastroentero-pancreatic (GEP) neuroendocrine system. The investigation was carried out with representatives of all vertebrate classes as well as with the protochordates Branchiostoma lanceolatum and Ciona intestinalis. The study revealed the presence of Pst-IR and Cg-IR cells in the gastro-intestinal mucosal epithelium as well as in the islet parenchyma of all vertebrates studied with the only exception found in rat. In the rat GEP system unequivocal immunoreactions were obtained only by the use of antiserum CgA/B. In the gastro-intestinal tract of the deuterostomian invertebrates no Pst-IR or Cg-IR cells could be observed with any of our antisera. Whether this might indicate that Pst-like or Cg-like peptides are characteristic for vertebrates or, more likely, whether similar proteins/peptides might be present in the alimentary tract of protochordates which do not react with the antisera at hand, remains to be clarified. Thouh pronounced interspecies and some intraspecies differences were found, several general conclusions can be drawn. In all vertebrate species, the Pst-IR and Cg-IR cells observed in the mucosal epithelium of the gastro-intestinal tract showed an endocrine structure and were of the so-called open type. The Pst and the Cg antisera which gave immunoreactions with parenchymal cells in the islets of Langerhans also reacted with cells in the epithelium of the pancreatic ducts. Comparative analysis of the reaction properties of the region-specific antisera used indicated that the Pst-like material in the islet cells of the cartilaginous fish species studied seems to be "mammalian-like," whereas it appears to be different in the other (phylogenetically younger) submammalian vertebrates. In addition, the Pst-like peptides in the gastro-intestinal mucosal epithelium and in those in the islets seem to differ in most submammalians. Finally, in the pyloric-duodenal junction of the quail (Coturnix c. japonica) the presence of a so far unknown peptide of the Cg family is presumed. In general, our results seem to indicate that the phylogeny of Pst-like and Cg-like peptides is not as "straight" as those which have been demonstrated for several other neurohormonal peptides.(ABSTRACT TRUNCATED AT 400 WORDS)