IMMUNOHISTOCHEMICAL IDENTIFICATION AND EFFECTS OF ATRIAL-NATRIURETIC-PEPTIDE, PANCREASTATIN, LEUCINE-ENKEPHALIN, AND GALANIN IN THE PORCINEPANCREAS

This study demonstrates the presence and distribution of atrial natriu retic peptide (ANP) pancreastatin (PST), leucine-enkephalin (Leu-ENK), galanin (GAL), and insulin in the pig pancreas. The effects of PST, A NP, Leu-ENK, and GAL on protein and amylase secretion were also invest igated to determine their functional role in the control of pancreatic secretion. PST-immunoreactive cells were observed in the islet of Lan gerhans and in the wall of the ducts. Leu-ENK-immunopositive cells wer e observed in both the endo- and exocrine pancreas. It is colocalized with insulin in the islet of Langerhans. ANP immunoreactivity was disc ernible in nerve fibers and cells of the exocrine pancreas. GAL-immuno positive cells were observed in close association with insulin-positiv e cells in the islets of Langerhans and in the exocrine pancreas. Stim ulation of isolated pancreatic segments with either ANP or Leu-ENK res ulted in increased protein secretion and amylase output. The Leu-ENK-e voked amylase secretion was antagonized by naloxone. Pancreastatin was effective at all concentrations, but low concentration had more marke d secretory effects whereas GAL failed to evoke any significant increa ses in either protein or amylase secretion. The results of the study h ave demonstrated a close association of peptidergic fibers with the se cretory cells of the pancreas. The nerve fibers can release peptides t hat in turn can stimulate protein and amylase secretion.