Pancreastatin was isolated from porcine pancreas in 1986 and has been shown to inhibit insulin release and exocrine pancreatic secretion in vivo. In the isolated perfused rat pancreas, we investigated its effect on the exocrine pancreas and evaluated its indirect effects mediated via the islet-acinar axis. In the presence of 16.7 mmol/L glucose, 20 pmol/L, 200 pmol/L, and 2 nmol/L pancreastatin reduced insulin release but did not affect exocrine pancreatic secretion stimulated by cholecystokinin (CCK), secretin, or bombesin. Pancreastatin also failed to affect unstimulated exocrine pancreatic secretion. In the presence of 1.7 mmol/L glucose, 200 pmol/L and 2 nmol/L pancreastatin inhibited glucagon release and potentiated CCK-stimulated exocrine pancreatic secretion. Inhibition of glucagon release and augmentation of exocrine pancreatic secretion may be independent phenomena, but they could be linked by the islet-acinar axis. Thus we speculate that a pancreastatin-induced inhibition of glucagon release may indirectly have caused augmentation of exocrine pancreatic secretion.