Control of pancreatic amylase release in vitro: effects of ions, cyclic AMP, and colchicine.

1. The time course and concentration-response relationship of amylase release from pieces of guinea-pig pancreas in vitro in response to bethanechol and pancreozymin was determined.2. Removal of Ca(++) from the medium had no effect on basal amylase release but abolished the stimulating effect on release of bethanechol.3. Elevation of the concentration of Mg(++) in the medium increased basal amylase release and reduced the response to bethanechol.4. Elevation of the concentration of K(+) in the medium increased amylase release; this effect was blocked by a concentration of atropine which blocked also the response to bethanechol.5. Cyclic AMP, dibutyryl cyclic AMP and theophylline failed to stimulate amylase release. Pancreatic cyclic AMP concentrations were found not to be increased by bethanechol, pancreozymin or an elevated concentration of K(+) in the medium.6. Colchicine had no effect on basal amylase release or the response to bethanechol or pancreozymin.7. It is concluded that the coupling of stimulus to secretion involves ionic control but that neither cyclic AMP production nor microtubular mechanisms play a major role in controlling exocytosis in the pancreatic acinar cell. These findings are discussed in relation to the stimulus-secretion coupling processes in other cells.