Pancreastatin is a 49 amino acid peptide that was first discovered in the porcine pancreas. It is found in many cells of the neuroendocrine system and is produced from the proteolytic cleavage of its precursor, chromogranin A. Pancreastatin has been localized to insulin-containing β-cells, glucagon-containing α-cells, and somatostatin-containing D cells of the pancreatic islet. Most circulating chromogranin A originates from chromaffin tissue, and it is believed that this may be the major (and indirect) source of circulating pancreastatin. Porcine pancreastatin levels have been shown to increase 50% in response to a meal, and perfused porcine pancreas pancreastatin was released in parallel with insulin. There was also a vagal component to its regulation since electrical stimulation of the vagus nerve also stimulated pancreastatin release. In humans, pancreastatin levels in blood increased in response to intraluminal infusion of a mixed meal or following glucose ingestion.