Pancreastatin-like immunoreactivity and insulin are released in parallel from the perfused porcine pancreas

Pancreastatin, a peptide isolated from the porcine pancreas, suppresses insulin release from pancreatic islets of the rat. Pancreastatin immunoreactivity has been localized to islet B and D cells in the porcine pancreas. We have developed a RIA for this peptide, using rabbit anti-porcine pancreastatin antibodies and 125I-Tyr-pancreastatin. Isolated pig pancreata were perfused with a nonrecirculating bicarbonate buffer solution containing 4% Dextran and 0.1% Albumin. Glucose (11 mmol/liter) induced a biphasic release of pancreastatin-like immunoreactivity (PLI). Electrical stimulation of the vagus nerves (8 Hz), as well as perfusion with acetyl choline (10(-6) mol/liter) in the presence of 5.5 mmol/liter glucose, also evoked prompt PLI responses. Furthermore, truncated GLP-1 (proglucagon 78-107; 10(-9) mol/liter) induced PLI release. All tested stimuli also elicited insulin secretion. To investigate whether the PLI measured could be ascribed to secretion of the low molecular weight pancreastatin (Mr 5,100) or to a possible precursor such as chromogranin A (Mr approximately 75,000), perfusates containing PLI were subjected to gel filtration on an Ultropac G3000SW column. All of the PLI was recovered at the elution position of the pancreastatin marker. In conclusion, PLI and insulin are released in parallel from the perfused porcine pancreas, exposed to stimuli known to affect insulin release.