Potentiating role of cyclic AMP in pancreatic enzyme secretion, demonstrated by means of forskolin

The role of cyclic AMP in the regulation of enzyme secretion by the rabbit pancreas has been investigated by means of forskolin, an activator of the catalytic subunit of adenylate cyclase. Forskolin increases the cyclic AMP level in isolated pancreatic acini in a dose-dependent way. Basal amylase release, however, remains unchanged. Forskolin potentiates the increase in amylase release induced by the C-terminal octapeptide of cholecystokinin (CCK-8). Potentiation is already apparent at hormone concentrations which are only marginally effective in stimulating amylase secretion. CCK-8 alone does not raise the cellular cAMP level, but it potentiates the forskolin-induced increase. In relative terms, potentiation is higher with decreasing concentration of forskolin. These results indicate that cAMP alone does not play a direct role in CCK-stimulated pancreatic enzyme secretion in the rabbit, but it potentiates enzyme secretion already stimulated through a cAMP-independent process.